m4p. An .m4p file is an AAC-format digital audio file with added digital rights protection.

machine control. 1. See 9-pin. 2. An option for Digidesign’s Pro Tools that allows control over, and synchronization with, external players and recorders.

machine room. A dedicated room in a studio designed to isolate devices (such as computers, hard drives, and tape machines) that might contribute to an increased ambient noise floor.

macro. A computer command that combines two or more other commands to accomplish a task. Macros simplify performing complex, multistep operations and allow a single command to automate certain operations.

MADI. Multi-channel Audio Digital Interface. An AES standard for interconnecting digital multitrack recorders and mixers. MADI supports transmitting up to 56 channels of audio information over a single coaxial or optical cable.

magnetic shielding. See shield.

magnetic tape. An analog storage format in which a magnetizable oxide coating is adhered to a thin plastic strip. Record/play heads are used to magnetize the oxide during recording and to “read” the stored magnetism when playing back. Audio information and computer data can be stored on magnetic tape.

magneto-optical. A storage format that combines magnetic and optical technologies. A laser is used to heat the disc medium, which is then polarized by an electromagnet to store the information. The cooled medium retains this polarity, which can then be read by a low-power laser.

main outputs. The primary audio output or outputs on a device, which carry the mono or left-right stereo output signal. On a mixer, the main, or master, outputs may include connections for inserting equalizers or dynamics processors, such as compressors or limiters.

mains. 1. AC power coming from the wall outlet. 2. The front-of-house or audience speakers in a PA system.

makeup gain. Gain that is available to amplify the signal at the final output stage of a device, usually in a dynamics processor, such as a compressor or limiter. Makeup gain allows the device to compensate for peak volume reduced when compression or limiting is applied.

manual. 1. Part of the documentation that comes with a device, which describes its operation, use, and specifications. 2. A keyboard on an organ, harpsichord, clavichord, or other instrument.

mapping. 1. A function that assigns incoming data to a target destination. For example, incoming MIDI Continuous Controller #42 data might be mapped to control modulation. 2. Assigning samples to the keys of a keyboard.

marker. An icon that can be used to store and recall a particular location in the timeline of a DAW or sequencer. Markers might be placed at the various sections of a song, such as the beginning of the verses, choruses, guitar solo, and outro, making it easy to navigate to the different parts during recording, editing, and mixdown. In some DAWs and sequencers, markers can be used to store additional information, such as zoom level, so that when a marker is selected, the song will not only navigate to the proper location, but will also zoom in to the specified level. See Figure M.1.

Figure M.1. Markers (a.k.a. memory locations) can be used to store a location in a song in a DAW for quick navigation. The markers in this example are arrayed across the top of the tracks. The menu at the right can be used to locate the session to the selected marker.

MAS. MOTU Audio System. A protocol developed by MOTU and licensed to third-party developers and manufacturers for integrating software synths and samplers and effects and processing plug-ins into the company’s Digital Performer DAW.

masking. The tendency of a loud sound with overlapping frequency content to a soft sound to cover up those frequencies in the softer sound. Masking is used as the basis for many audio data compression schemes.

master. 1. The device that is providing the synchronization and timing information for the slave devices in a system. 2. The clock that provides the digital clock for synchronizing a digital audio system’s sample rates. See also master clock. 3. The MIDI keyboard or other controller that is providing the MIDI notes and other information for the slave devices in a MIDI system. See also controller keyboard. 4. The final, finished version of an audio production. 5. The process of preparing a recording for duplication or distribution. See also mastering.

master clock. The clock that provides the synchronization signal for a digital audio system. A master clock can be either a standalone device or the clock built into one of the devices in the system. The master clock controls and defines the sample rate for the system. See also word clock.

master fader. A fader (or faders) in the master section of a mixer that sets the level for the final summed mono, stereo, or multichannel surround output.

mastering. The process of optimizing a recording for distribution in various formats and preparing it for duplication. Mastering can be thought of as the last stage of audio production and the first stage of distribution and manufacturing. Mastering consists of editing, equalizing, and processing the dynamics of a recording, fading it in and out and setting its level so that it will flow well with other songs on an album, maximizing the volume level, and otherwise tweaking the recording to provide the best sound quality and listening experience for consumers.

master keyboard. See controller keyboard.

master volume. The final level control in a signal path, which sets the overall output level.

matrix editor. See piano roll.

matrix mixer. A type of mixer where any input can be routed to any output, and in some cases the EQ and the level for each input’s feed to each output can be controlled. Matrix mixers are often used for creating multiple independent monitor mixes to be sent back to musicians during a live performance onstage.

matrix modulation. A feature of some synthesizers where any modulation source can be routed to control any destination parameter.

matrix surround (a.k.a. Dolby surround). An analog surround format in which the rear left and right channels are encoded into the front left and right signals and are partially decoded on playback. Because the surround channels can only be partially decoded from the front channels, matrix surround is not as effective as digital systems in which the surround channels are stored as discrete signals. See also Dolby.

maximizer. A device or plug-in that uses a compressor or limiter to raise the level of an audio signal as high as possible without distortion (though reduction of peaks will often occur and can be pushed to such an extent that audible distortion will result).

maximum SPL. A microphone specification that indicates the highest sound pressure level a microphone can handle without distorting. The electronics in the mic will distort first, so some microphones contain a pad that can be used to reduce the electronic signal level, allowing higher acoustic sound pressure levels to be handled. The maximum SPL spec is referenced to 0.5% distortion at 1 kHz.

maximum transfer rate. See burst transfer rate.

Mb. Megabit (1,048,576 bits).

MB. Megabyte (1,048,576 bytes).

Mbps (a.k.a. Mb/s). Megabits per second or 1,000,000 bits per second.

MBps (a.k.a. MB/s). Megabytes per second or 1,000,000 bytes per second.

MDF. Medium-Density Fiberboard. A wood product made from processed wood fibers combined with resin, and used wherever real wood might be used, such as in monitor and speaker cabinets, guitar and bass amplifiers, PA speakers, and more.

MDM. See modular digital multitrack.

mean time before failure (a.k.a. MTBF). Manufacturer spec for how long a drive will last, usually measured in hours of operation.

median plane. The center line between the left and right speakers in a studio monitor setup. The ideal listening position will be on the median plane, equidistant from the two speakers and at the same distance from the speakers as the speakers are spaced apart (forming an equilateral triangle among the two speakers and the listener).

medium-diaphragm microphone. A microphone with a diaphragm measuring somewhere around 5/8- to 3/4-inch in diameter. A medium-diaphragm microphone will deliver response that falls between small-diaphragm and large-diaphragm mics, with good transient detail and full sound.

mega. 1. A prefix meaning one million. This definition is often used for data transfer rates—a megabit transfer rate would mean 1,000,000 bits per second. 2. In computer storage terms, 2 to the 20th power, or 1,048,576, since computer storage media use base 2 or binary mathematics.

megabit. A measure of computer storage indicating 2 to the 20th power bits (1,048,576 bits).

megabyte. A measure of computer storage indicating 2 to the 20th power bytes (1,048,576 bytes).

megahertz. A million hertz or cycles per second.

Mellotron. A keyboard instrument introduced in 1962. The instrument’s sounds were contained on racks of short analog tapes with one tape per key. When a key was pressed, its tape played a 6- to 8-second recording of a sound. A spring rewound the tape when the note was released. To play a note longer than six to eight seconds required releasing the key and quickly restriking it. Sounds could be changed by installing new racks of tapes. The Mellotron can be thought of as an early analog sampler.

membrane trap. Type of bass trap that features a thin membrane, panel, diaphragm, or surface that vibrates in response to low-frequency sound waves and absorbs the sound energy.

memory effect (a.k.a. battery memory, lazy battery effect). A tendency of nickel-cadmium batteries to be unable to reach full charge if they are recharged without being fully discharged. In most cases, memory effect can be circumvented by completely discharging and fully recharging a battery several times.

memory location. See marker.

menu. Graphical computer programs and operating systems save screen space by organizing commands into sets of related options that can be accessed as necessary by dropping down a hidden part of the window to reveal the available commands. Clicking on a command in a menu or typing in its key shortcut causes it to execute. See Figure M.2.

Figure M.2. A program’s or operating system’s menus organize the available commands into lists. Submenus branch off from the main menu and provide related command options.

menu structure. The manner in which a program’s or operating system’s commands are arranged into menus, including submenus that may branch off of the main menu.

merge (a.k.a. merge file). A DAW command that creates a new audio file by combining two or more existing audio files. The merge function is especially useful for combining a number of short audio regions resulting from editing a track into a new, single audio file that is easier to manage.

metadata. Literally, data that describes other data. Digital audio metadata may include information such as number of channels, sample rate, bit depth, type of data encryption, and more. Metadata is typically stored in a part of a file called a header that an application can access to “learn” about a file.

meter. 1. An indicator on an audio device or in an audio program that displays signal level or other information. 2. The arrangement of stressed and unstressed beats in music.

meter bridge. In a mixing console or multitrack tape recorder, an array of meters that indicate the level of input channels and various outputs. In some cases, a meter bridge is built into the chassis of the unit; in other cases, the meter bridge is a separate option. Some DAWs offer a virtual version of a meter bridge, displaying a number of meters within a window. See Figure M.3.

Figure M.3. MOTU’s Digital Performer DAW software offers a virtual meter bridge for displaying signal levels.

metronome. A device that indicates musical tempo by audibly clicking and/or flashing a light at a user-specified rate.

MF. Midrange frequency.

MHz. Megahertz.

MI. Music Industry. A term used in reference to manufacturers and retailers of musical instruments.

mic amp. See mic preamp.

mic level. The amount of electrical signal level generated by a microphone. Mic levels can range from a few millivolts to 100 millivolts, often falling around –40dBu. Because of these extremely low levels, microphone signals must be preamplified in order to be used with the line-level gear that makes up most signal chains. See also mic preamp.

mic preamp (a.k.a. microphone preamp, mic, amp, preamp). At its most basic, a type of amplifier used to raise a mic-level signal to line level (either 0.316 volts or 1.23 volts). Mic preamps can be either standalone pieces of hardware or built into a mixer, audio interface, or other device. Features sometimes found in mic preamps including input impedance switching, pads, polarity reverse, and more. Many mic preamps also include instrument-level inputs.

microchip. See IC.

microdrive. A trademarked brand name for a miniature one-inch hard drive designed to fit in a CompactFlash Type II slot.

micron (a.k.a. micrometer). One millionth of a meter, or 0.000039 inches. A human hair measures about 50 microns. A microphone diaphragm can be as thin as just a few microns.

microphone (a.k.a. mic). A transducer that converts sound waves into electrical signals. A variety of types are available, including condenser, dynamic, ribbon, piezo, and others.

microphonic. A component in a signal path that produces audio when it is vibrated. Vacuum tubes are the most common component to become microphonic, though cables and other components are also susceptible.

microsecond. One millionth of a second or one thousandth of a millisecond.

MID. See Standard MIDI file.

middle C. A note tuned to 261.1 Hz. The MIDI Specification defines middle C as note number 60.

MIDI. Musical Instrument Digital Interface. A protocol developed jointly in the early 1980s by several manufacturers that allows various pieces of music and audio gear to communicate with and control each other. MIDI is a digital protocol that represents and transmits performance “gestures,” such as a key press or control change, as well as various types of synchronization and other data. No audio is carried over MIDI, though samples can be transmitted (very slowly) between devices.

MIDI cable. A three-conductor cable terminated with five-pin DIN connectors. (The outer two pins are not used.) Each MIDI cable carries 16 logical channels in one direction with a 31.25-kb bandwidth. MIDI uses balanced connections and telescoping grounds to enhance stability and to prevent ground loops. The maximum length for a MIDI cable defined by the MIDI Specification is 15 meters, though in practice, most users try to keep MIDI cables as short as possible, and usually less than 30 feet in length.

MIDI channel. A method for organizing MIDI data or messages. The MIDI Specification defines 16 channels, number 1 though 16. Each channel can carry any of an array of possible channelized messages. A device can be set to transmit on a particular channel (similar to a radio or television transmitter). Only devices that are set to receive that channel will respond to those messages (similar to a radio or television receiver).

MIDI channel messages. A type of MIDI message that is coded with a particular channel number and is intended to be received only by devices “tuned” or set to that channel. Examples include MIDI notes, monophonic and polyphonic after-touch, pitch bend, continuous controllers, program change, and others.

MIDI channel mode. One of four ways in which a device can be configured to respond to incoming channel messages. There are two aspects to channel modes: omni on/off, which sets how the device responds to information on incoming MIDI channels; and poly/mono, which sets how the device responds to multiple note messages received simultaneously (whether it will be polyphonic—where it will sound chords or multiple notes simultaneously—or monophonic, where it will only play one note at a time). See Table M.1.

MIDI clock. A timing reference carried by MIDI that runs at 24 PPQN. The speed of the MIDI clock varies with a song’s tempo so that each quarter note receives 24 evenly spaced pulses, regardless of the tempo. MIDI clock is not a form of time code, as it does not carry song or time location information and it varies in speed.

MIDI continuous controller (a.k.a. CC). The MIDI Specification provides for 128 different messages (numbered 0 through 127) per MIDI channel that can be used to carry control, switch, and parameter changes. Each continuous controller has a range of values from 0 through 127. In some cases, two continuous controllers can be used together to provide coarse and fine control, though not all devices will respond to fine controls. Continuous controllers can be used to add expressiveness to a sequence or to capture the various performance gestures made by a musician. The MIDI Specification defines a number of continuous controllers for particular applications. Table M.2 shows some of the common continuous controller assignments. (Note that pitch bend is not a continuous controller, as it requires higher resolution. Pitch bend is its own type of MIDI message.)

MIDI control change. See MIDI continuous controller.

MIDI controller. 1. A keyboard or other device that generates MIDI note or control information. 2. See MIDI continuous controller.

MIDI date rate. The rate at which MIDI information is transferred between devices using MIDI cables: 31.25 Kbits per second, with 10 bits transmitted per byte (a start bit, eight data bits, and a stop bit).

MIDI delay. 1. The amount of time it takes for a MIDI message to enter a device through its MIDI in port and to exit through its MIDI thru port. If a receiving device is at the end of a long daisy chain of devices, the delay may accumulate enough to be noticeable. 2. The time it takes for a device to respond to an incoming MIDI message (though there are other factors in this besides MIDI, such as processor speed).

MIDI echo. A function of some devices in which data entering the device’s MIDI input is sent out the MIDI output. (Normally, data received by a device’s MIDI input is only sent out through its MIDI thru port.)

MIDI implementation chart. A part of a device’s documentation typically found in the back of its manual that lists what MIDI messages and data the device can transmit and respond to. This information is organized into a standard chart format that makes it easy to see what MIDI functions the device supports. See Figure M.4.

Figure M.4. A device’s MIDI implementation chart shows what MIDI messages the device can transmit and recognize.

MIDI in. One of the three possible types of MIDI ports. A MIDI in port receives messages and data from an external sequencer or controller. A MIDI in port can be fed by either a MIDI output or a MIDI thru.

MIDI interface. A peripheral device that allows a computer to receive and transmit MIDI messages and data. MIDI interfaces may be internal expansion cards or external boxes that connect via serial or parallel ports, or using USB or FireWire. Many modern MIDI devices support direct connection to a computer using USB, so MIDI interfaces are not as necessary as they were before the advent of USB. A MIDI interface may have one or more MIDI input and output, each of which can carry 16 channels of information. This means that a two-input/two-output MIDI interface could carry 32 MIDI channels in and out of the computer. An eight-input/eight-output MIDI interface could carry 128 MIDI channels in and out of the computer. Some MIDI interfaces also incorporate extended functions, such as SMPTE time code synchronization, machine control functions, MIDI merging, MIDI filtering and processing, MIDI routing and patch bay functions, and more.

MIDI learn. A function of some software, where a virtual control can “learn” to respond to an incoming MIDI continuous controller message from a hardware controller by selecting the desired virtual control, then moving the desired hardware control. This makes it fast and easy to configure a piece of software to work with a control surface or controller keyboard.

MIDI log jam. A situation that occurs when the amount of data to be transmitted by a single MIDI cable exceeds the available bandwidth. Typically, overuse of continuous controllers and pitch bend is to blame. MIDI log jam can be thought of as MIDI overload and can result in timing errors, stuck notes, glitching continuous controllers, and other symptoms.

MIDI Machine Control (a.k.a. MMC). A set of MIDI messages used to control playback and other functions in hardware recorders and players. MIDI Machine Control commands include play, stop, rewind, fast-forward, and others. MIDI Machine Control, when used in conjunction with MIDI Time Code, allows a MIDI sequencer to control a recorder as well as synchronize to it.

MIDI merge. A function of some devices that allows the device to combine two or more streams of MIDI information into a single stream.

MIDI merger. A device that combines two or more streams of MIDI information into a single stream.

MIDI mode. See MIDI channel mode.

MIDI note. A two-part MIDI channel message. The first part of a MIDI note is the note on message, which is sent when a key is struck and tells the receiving device to begin sounding the note. There are three main parts to the note on message: the MIDI channel, the MIDI note number to be played, and the MIDI velocity for that note. The second part of a MIDI note is the note off message, which is sent when the key or sustain pedal is released and tells the receiving device to stop sounding the note. There are three main parts to the note off message: the MIDI channel, the MIDI note number to be stopped, and the MIDI release velocity for that note. The MIDI channel and MIDI note number must match in both the note on and note off messages for the note to be properly stopped.

MIDI note number. A MIDI channel message that specifies which musical note has been played. There are 128 possible MIDI note numbers, ranging from 0 through 127. (Though some manufacturers frustratingly decide to use 1 through 128 for the note range.) Middle C is defined to be MIDI note number 60 by the MIDI Spec.

MIDI out. One of the three possible types of MIDI ports. A MIDI out port carries messages and data generated inside a device by playing keys, hitting pads, playing a sequence, moving a controller, and so on. A MIDI out port is connected to the MIDI in port of another device to allow the first (master) device to control the second (slave) device.

MIDI pan. MIDI Continuous Controller #10, a MIDI channel message that is defined to control the pan setting of a device or a multitimbral part that is set to respond to a particular MIDI channel.

MIDI part. An independent section of a multitimbral synthesizer or sampler that can respond to its own MIDI channel. See multitimbral.

MIDI port. A MIDI jack. There are three types: input, output, and thru. See Figure M.5.

Figure M.5. There are three types of MIDI ports or jacks: MIDI inputs, MIDI outputs, and MIDI thrus.

MIDI program change. See program change.

MIDI through. See MIDI thru.

MIDI thru (a.k.a. MIDI through). One of the three possible types of MIDI ports. A MIDI thru port carries a copy of the messages and data that are arriving at the MIDI input of the device. A MIDI thru port can be connected to the MIDI in port of another device to create a daisy chain.

MIDI Time Code (a.k.a. MTC). A version of SMPTE linear time code carried over MIDI and used to synchronize compatible devices, such as sequencers to other pieces of gear.

MIDI time stamping (a.k.a. MTS). A MIDI recording and transmission technique developed by MOTU, where each piece of data is “stamped” or encoded with a specific time location. This provides for extremely accurate playback from a sequencer that is not dependent on a clock or the sequencer’s PPQN resolution.

MIDI volume. MIDI Continuous Controller #7, a MIDI channel message that is defined to control the volume of a device or a multitimbral part that is set to respond to a particular MIDI channel.

midrange. Literally, the middle part of a frequency range. There is no exact range of frequencies defined within the range of human hearing as the “midrange”; it falls somewhere between the low frequencies and the high frequencies.

mid-side stereo. See MS stereo.

millisecond (a.k.a. ms). 1/1,000 of a second.

milliwatt (a.k.a. mw). 1/1,000 of a watt.

minijack. A 1/8-inch audio jack, either TS (unbalanced) or TRS (either balanced or dual-channel). The female counterpart to a miniplug.

minimum system requirements. The minimum computer power and amount of RAM, along with the minimum OS version, hard drive space, and any peripherals or requirements necessary to run a piece of software.

miniplug. A 1/8-inch audio plug, either TS (unbalanced) or TRS (either balanced or dual-channel). The male counterpart to a minijack.

mini-TOSLink. An optical connector type found on Apple computers and some other audio gear that resembles a minijack, but is slightly longer. See also TOSLink.

mix. 1. Creating a blend and proper balance of the sounds that make up a performance or recording. 2. A blended combination of sounds that comprise a performance or recording. 3. A control (sometimes labeled “wet/dry”) that is used to set the blend for dry and effected signals in an effects processor.

mixdown. The final stage of producing an audio project in a studio, where individual tracks and signals are combined and processed to create a finished recording, whether mono, stereo, or surround, that will be sent to mastering for preparation for distribution.

mixed-mode disc. An audio CD that also contains computer data. See Blue Book.

mixer. At its most basic, a device or software function for combining audio signals. Mixers frequently contain sophisticated audio routing and processing capabilities. Mixers can range from extremely basic units to one containing extended functions and features, including microphone, instrument, and line preamps; equalization; subgrouping; aux and effects sends and busing; monitor control; talkback; input switching; headphone amps; level automation; and more.

mixing board. See mixer.

mixing console. A large-format, desk-style mixing board. See mixer.

mixing desk. U.K. term for mixing board. See mixer.

mix-to-disk (a.k.a. bounce to disk). A function in some DAWs that allows a mix to be recorded directly to a file on a hard disk without routing it to an external recorder or to new tracks. The mix-to-disk function can also be used to bounce sub-mixes to new audio files that can then be imported to new tracks.

mLAN. Music Local Area Network. A Yamaha-developed protocol for networking music and audio gear and computers using FireWire cables and ports. Up to 127 devices can be connected in daisy-chain fashion; devices can be hot-plugged and unplugged. Each cable can carry thousands of MIDI channels of information and more than 150 digital audio channels of information (at 24-bit/48-kHz resolution). Though there are more than 100 manufacturers in the mLAN Alliance, the protocol has yet to be widely adopted.

MLP. Meridian Lossless Packing. A technology, developed by Meridian Audio and licensed to Dolby Laboratories, for lossless audio compression on DVD Audio. MLP can reduce the data rate for 24-bit/96-kHz 5.1 surround audio from 13.8 MB/second to under the 9.6 MB/second maximum DVD-Audio transfer rate and can reduce audio file sizes by 30 to 50 percent.

MMA. MIDI Manufacturers Association. A group of manufacturers of MIDI-compatible equipment that is responsible for developing the MIDI standard. www.midi.org.

MMC. See MIDI Machine Control.

MME. Multimedia Extension. An older type of Microsoft Windows OS driver developed for Windows 3.0 and used for audio and video hardware. MME drivers were replaced by WDM and other lower latency driver types in more current versions of Windows.

MOD. A file format that includes MIDI sequence information and sample playback data. Since the MOD file can contain samples, which can be used either as loops or instrument notes, playback can be consistent no matter what computer the file is played on.

mod wheel. Short for modulation wheel. A wheel, paddle, or stick control found on synthesizers and samplers that is typically internally mapped to control vibrato or some other form of modulation. MIDI Continuous Controller #1 is usually also sent, which is defined to control modulation.

modal. Pertaining to room modes.

modal distribution. How room modes are spaced across the frequency range. See also room mode.

mode. 1. A particular setup in a device that allows for certain types of operation or functions. Examples include edit mode, disk mode, performance mode, and others. 2. An acoustic resonance in a room. See room mode. 3. A musical scale that is derived from another scale.

model. A computer representation of a real item or process.

modeling. In audio, the use of mathematical equations to re-create or represent sounds or processes. Complex computer algorithms are used to imitate the behavior of analog circuits and acoustic properties.

modes of vibration. See room mode.

modifier keys. Keys on a computer keyboard that change the function of other keys when held down. With text, a key may create one character when pressed by itself, a capitalized version of that letter when pressed while the Shift key is held, another character when the Option key is held, and another when the Control key is held. Combinations of modifier and regular keys are also used as shortcuts for accessing commonly used commands, such as Save and Quit.

modular digital multitrack (a.k.a. MDM). One of several types of 8-track digital recorders (tape- and hard disk–based) that could be locked together to create larger systems with more tracks—they were all the rage in the ’90s. There are still many thousands of these recorders out there, being used every day by studios around the world. Many pro studios keep a few around for compatibility reasons, or for doing transfers for clients from digital tape to a computer-based DAW.

modular synthesizer. An analog synthesizer that is made up of a number of independent modules, each of which provides a particular function, such as oscillator, filter, envelope generator, amplifier, and so on. The audio and control signals accepted and generated by the various modules are routed using short patch cables.

modular unit. See rack unit.

modulation. Literally, change. 1. A change in a signal or the value of a parameter that occurs in real time, as the signal is passing through the device. 2. MIDI Continuous Controller #1, which is defined as the modulation wheel and is often routed to vibrato (frequency modulation) or another form of modulation. 3. In music, a key change.

modulation noise. Irregularity in a signal that sounds like noise. With analog tape, modulation noise is caused by the non-uniformity of the magnetism. In digital systems, quantization errors result in modulation noise.

modulation wheel. See mod wheel.

module. A tabletop or rackmount synthesizer or sampler that does not have keys of its own. Modules are intended to be controlled and played through MIDI, but otherwise are identical to keyboard synths and samplers.

MOL. Maximum Output Level. A specification for audio equipment, especially analog tape machines, that is standardized as the level a device can put out with 3% harmonic distortion and 3% intermodulation distortion. To truly be useful, MOL needs to be stated or graphed versus frequency.

momentary switch. A switch that does not latch when depressed or flipped. When the switch is released, it automatically reverts back to its default state. Sustain pedals, talkback switches, and other controls typically use momentary switches.

monaural. A single-channel audio signal. See also monophonic.

monitor. 1. To listen to audio via speakers. 2. Studio speakers, usually optimized for “flat” frequency response. See also reference monitor. 3. A speaker or headphones intended for the musicians to use to hear themselves and each other when recording or performing live. 4. A computer screen or display.

monitor controller. A standalone device that includes the functionality of the monitor section of a mixing console, and is intended for use in mixer-less DAW-based studios. Monitor controllers typically offer speaker switching for two or more sets of monitors, monitor level control and calibration, headphone outputs, and input selection for monitoring different sources. Some models add talkback and dim functions, as well as cue functions for musician headphone mixes.

monitor send. A bus used to send a mix to musicians onstage or in a studio so they can hear themselves and each other.

mono. See monophonic.

mono bridged. See bridged.

mono-compatible. A stereo or surround audio signal that maintains its phase and blend integrity when summed to a single channel.

Mono mode. An expanded version of MIDI Channel Mode 4 (Omni off/Mono). Mono mode was originally designed for MIDI guitar applications, where each string was transmitted on a separate MIDI channel. This allows each string/channel to pitch bend independently and to have its own preset. See also MIDI channel mode.

monophonic. 1. Also known as mono. An audio signal consisting of a single channel. 2. An instrument capable of playing only one note at a time.

monophonic aftertouch (a.k.a. channel aftertouch). A type of MIDI aftertouch in which a single value is transmitted for each channel. If a chord is played, the highest aftertouch value for all the held keys is the one that is transmitted for all the keys. See also aftertouch.

mono summing. Collapsing a stereo or surround signal into a single channel. This is often done to check for phase problems and balances within a mix.

more me. 1. The tendency of musicians to always want to hear themselves loudest in a mix, especially in a monitor or headphone mix when recording. 2. A type of headphone monitor system that allows the musician to add more of himself to his headphone mix.

morphing. 1. A real-time technique for smoothly transitioning from one thing to another. Morphing was originally a video effect that has since been adapted to audio and other media. Morphing is more than simply crossfading from one signal to another. Rather, the beginning sound is processed to gradually convert it into the ending sound, with the intermediary steps audible as the transition occurs. 2. In effects processors, smoothly transitioning from one preset or setting to another, with all the parameters simultaneously changing to create the new setting.

MOSFET. Metal Oxide Semiconductor Field Effect Transistor. A common type of FET often used in audio circuits. MOSFETs are similar to JFETs, though they are made of different materials, and MOSFETs have an insulating oxide that is not present in JFETs. MOSFETs are often used in both digital and analog audio circuits. See also FET, JFET, transistor.

motherboard. A printed circuit board containing the primary components in a microprocessor-based device, such as the CPU, RAM, ROM, and more.

motorized fader. A fader with an integrated motor that can move the fader in response to automation data. See moving fader, moving fader automation.

mount. With computers, to “mount” is to a make a hard drive or other storage media accessible by the CPU. Mounting consists of reading the media’s file structure and ensuring it is compatible with the computer.

MOV. Metal Oxide Varistor. An electrical component that changes resistance based on incoming voltage. MOVs are often used in surge protectors; as the voltage on the AC line increases, the MOV resistance increases, protecting any connected equipment from excessive voltage.

moving coil. A technology used in microphones, phono cartridges, and other transducers for converting motion to electrical signals or vice versa. In a dynamic microphone, a coil of wire is attached to the diaphragm. When the diaphragm moves in response to sound waves, the coil is also moved within a magnetic field. The motion of the coil generates an alternating-current electrical signal that represents the sound waves. A speaker works in exactly the opposite way; electrical signals cause a coil of wire that is attached to a cone in a magnetic field to move, creating changes in air pressure our ears perceive as sound waves.

moving fader. A motorized fader that moves in response to automation data. See also moving fader automation.

moving fader automation. A hybrid digital/analog system found in hardware mixers that uses automation data to control the physical movement of motorized channel faders through which analog audio is passing. Since the levels were being changed by actual faders rather than by VCAs, some engineers felt that moving fader systems sounded better, though modern VCAs have improved to where this isn’t an issue. Some control surfaces and digital mixers have motorized faders that move in response to automation, but this isn’t the same thing as moving fader automation, as the analog audio doesn’t actually pass through the faders.

MP3 (a.k.a. MPEG-1 Audio Layer 3). A part of the MPEG-1 standard that specifies a lossy audio compression format that has been widely adopted by manufacturers and consumers for file storage and playback. MP3 can reduce the CD data rate (1,411 kbits/second for stereo) down as low as 32 kbits/second, while maintaining a 44.1-kHz sample rate.

MPC. AKAI abbreviation for MIDI Production Center or Music Production Center. The original MPC60 was a standalone sampling drum machine/MIDI sequencer combination launched in 1988 and designed by Roger Linn. Subsequent models have added a variety of capabilities, including built-in virtual analog synths, multitrack audio recording, effects, and more.

MPEG. Moving Pictures Experts Group. An organization that develops standards for audio and video digital compression encoders/decoders. www.mpeg.org.

MPU-401. Abbreviation for MIDI Processing Unit 401. A type of MIDI interface developed by Roland for PCs around 1984 that evolved into a standard. The original MPU-401 consisted of a computer expansion card that connected to an external box containing MIDI in, out, and thru; tape in and out; and MIDI sync ports. There were a variety of descendants to the original MPU-401 over the years. Support for the MPU-401 standard was finally removed from Windows with the release of Windows Vista (though some other operating systems still support it).

ms. Abbreviation for millisecond (with lowercase “m” and “s”). One-thousandth of a second.

MSB. Most Significant Bit (though technically “MSB” in all caps would refer to “Most Significant Byte”). The bit in a digital word that has the most impact on the mathematical value of the word—typically the leftmost bit.

M-S stereo (a.k.a. mid-side stereo). A stereo miking technique using two coincident microphones—one in cardioid (though omni and other patterns are sometimes used) pattern facing toward the source and one in figure-8 pattern faced at 90 degrees to the source. The figure-8 mic is split to feed two mixer channels, one of which is reversed in polarity. By combining the cardioid mic with the two figure-8 signals and varying the balance of the channels, the stereo width of the resulting sound can be changed. M-S stereo signals are 100% mono-compatible; when the stereo signal is summed to mono, the two out-of-phase figure-8 “side” signals cancel each other, leaving only the mono “mid” mic signal. See Figure M.6.

Figure M.6. M-S stereo is a miking technique that uses coincident cardioid and figure-8 mics. It allows the engineer to adjust the stereo width of the recording and provides complete mono-compatibility.

MTBF. See mean time before failure.

MTC. See MIDI Time Code.

MTC quarter frame. A message that allows subframe accuracy from linear time code sent over MIDI. Four quarter-frame messages are sent per frame, each containing a time-code stamp.

MTS. See MIDI time stamping.

mu. 1. See gain. 2. A ratio of change in voltages within a vacuum tube that determines its amplification and therefore the gain of a stage in a circuit.

mult. Short for multiple. 1. A passive signal splitter, usually in a patchbay. Several jacks on the bay are wired together so that a signal entering one jack will simultaneously feed the other jacks. See also normal. 2. An audio engineering term for splitting an output signal so it can feed multiple inputs simultaneously.

Multi mode. A term used by some manufacturers for the mode in which a synthesizer or sampler operates as a multitimbral device.

multiband compressor. A device, program, or plug-in that separates the audio range into bands of frequencies, then uses independent compressors to process each band independently. For example, a multiband compressor with three bands would separate the audio range into low-, mid-, and high-frequency bands using a crossover. A separate built-in compressor could then be used to process each band, allowing different compression amounts, thresholds, and parameters to be applied to the three bands. A multiband compressor can be thought of as a sort of “dynamic” equalizer. Multi-band compressors can be used to shape the overall sound of a track, to tame a troublesome range of frequencies, for de-essing, and for other applications. See Figure M.7.

Figure M.7. A multiband compressor splits the audio into separate bands of frequencies, each of which can be processed with an independent compressor.

multiband limiter. A processor that separates the audio range into bands of frequencies, then uses independent limiters to process each band independently. See also multiband compressor.

multichannel. Literally, more than one channel, though in practice usually referring to more than two channels of audio. The term is used in a variety of ways; one example would be to describe a processor that can effect two, four, or more channels of audio independently.

multi-client. A function of some software drivers that allows more than one application to access a peripheral device simultaneously.

multi-core. A die or chip containing more than one computational core processor. Additional cores may or may not increase computational speed depending on the application, but they will increase the ability to multitask. See also core.

multi-effects. An effects processor that can produce multiple types of effects simultaneously.

multi-FX. See multi-effects.

multimedia. One of any number of art forms that combines more than one medium or discipline, including combinations of music, graphics, dance, drama, video, and others.

multi-mode filter. Some filters can only produce one type of filtered output: high-pass, low-pass, band reject, and so on. A multi-mode filter can produce several types of filtered outputs simultaneously.

multi-pattern microphone. A microphone that can be switched to use one of several polar patterns. Most multi-pattern microphones utilize dual diaphragms that are electronically combined to create the various patterns.

multiplex. To encode signals so that more than one can be transmitted down a single channel or cable simultaneously.

multi-sample. A collection of related samples that comprise a single preset or sound in a sampler or sample-playback synthesizer. For example, a piano “sample” or sound might consist of a separate sample (or even layer of several samples) for each note on the keyboard. (More commonly, to conserve memory and processing resources, each sample in a multi-sample will cover a range of several musical notes.) Multi-sampling is designed to prevent or at least reduce the problem of samples changing in timbre as they are pitched up or down by limiting how far each sample must be transposed.

multisession. A compact disc that conforms to the Orange Book standard. Multisession CD-Rs are discs that have been burned but are still “open,” meaning that more data can be added to whatever data is already stored on the disc. Once the disc is “closed” or “fixed,” a TOC (Table of Contents) is added. At that point, the CD-R becomes a Red Book–compatible CD if it contains audio tracks or a Yellow Book–compatible CD if it contains data.

multi-tap delay. A type of stereo delay where the user can specify more than one time interval at which discrete echoes will occur. A multi-tap delay can be thought of as many separate delay lines within a single hardware or software processor, each with its own delay time, output level, panning, and feedback amount.

multitasking. A device that is capable of performing more than one function or process simultaneously. In computers, multitasking refers to the operating system’s ability to run more than one program simultaneously. The OS is able to do this by scheduling which task is running, and maintaining a queue of tasks or operations that are waiting to be performed. (The switch from one task to the next is called a context switch.) There are three approaches to computer multitasking:

multithreading (a.k.a. parallelism). A type of computer program that can nearly instantly switch between multiple streams of operations, or “threads,” giving the appearance that more than one stream of instructions is occurring simultaneously. Multithreading also allows the processor to operate more efficiently; for example, if a particular thread is waiting for data in order to continue processing, the OS can switch to working on a thread that has data available. Unlike multi-processing systems, which use multi-core processors, multi-threading takes place on a single processor. Multiprocessing systems can also run more than one program at a time, while multi-threading takes place in one program and utilizes one cache and buffer for all the threads. The disadvantage to multi-threading is that multiple threads can conflict with one another, and the execution of any single thread may be slowed (while the overall speed of executing all the threads may be increased). Multi-threading and multiprocessing are complementary and are often combined, such as in multi-core computers that are capable of multi-threading. See also multitasking.

multitimbral. A function of some synthesizers and samplers that allows the instrument to produce more than one sound (timbre) simultaneously. The device is split into multiple independent virtual parts, each of which can play back notes over a separate MIDI channel using a different preset or patch. See Figure M.8.

Figure M.8. A multitimbral synth or sampler can be divided into virtual “parts,” each of which can have its own sound or preset and can respond to its own MIDI channel.

multitrack. 1. Literally, more than one track. 2. An analog or digital recorder that is capable of recording and playing many independent signals simultaneously. 3. A recording consisting of multiple tracks containing independent parts and performances that must be mixed to create a final piece of music or other final audio production. 4. The process of recording a piece of music by using multiple tracks to store independent parts and performances that are later combined at mixdown.

music. Though there are probably as many definitions for “music” as there are musicians and listeners, the most literal definition is likely “organized sound.”

mute. 1. To turn off an audio signal or channel. 2. A control on a mixer or other device that turns off or silences a signal or channel.

mute group. A function in some hardware and software mixers that allows a single button to mute and unmute a selected group of channels simultaneously.

Mylar. A brand or trade name for thin polyester film developed by DuPont in the 1950s. Mylar offers good strength and light weight, making it ideal as the base material for microphone diaphragms and headphone drivers.