vacuum tube. An electronic component that features electrodes (anode or plate and filament or cathode) inside a glass tube from which all the air has been removed, creating a vacuum where electrons can easily flow. Additional items inside the tube, including the grid, are used to control the electron flow and therefore the current, or amplification, the tube is providing.
vaporware. A product that has been announced by a manufacturer but that has not yet shipped or become available to end users.
variable bit rate (a.k.a. VBR). Audio data compression algorithms that vary in response to the input signal. The bit rate is increased when necessary to accurately represent the input signal, and it is reduced when the input can be represented with a lower rate. Variable bit rate algorithms generally provide better quality while using less space than constant bit rate (CBR) algorithms.
variable mu. A type of tube with the ability to decrease gain as the level of the input signal increases. In audio, variable mu designs are used in certain compressors.
variable pattern microphone. A microphone with a switchable or continuously variable polar pattern. In most cases, a variable pattern mic will have dual diaphragms, which are combined electronically to create the various patterns.
varispeed. A feature of analog tape decks (that has been emulated by DAWs) that changes the speed of the tape during recording and playback. Increasing the speed makes the audio play faster and raises the pitch. Conversely, reducing the speed lowers the pitch and plays the audio back more slowly.
VAST. Variable Architecture Synthesis Technology. A synthesis system developed by Kurzweil for the company’s K-series synthesizers (K2000, K2500, K2600, and so on). VAST uses algorithms to reconfigure how the oscillators and other synth “modules” are arranged and connected. The VAST engine also provides numerous modulation and processing capabilities for creating expressive and complex sounds.
VBR. 
See variable bit rate.
VCA. Voltage Controlled Amplifier. An amplifier circuit where the output gain can be controlled using an external voltage. VCAs are common in analog synthesizers, where they can be controlled by envelope generators to shape the volume of sounds. VCAs are also used in some dynamics processors, such as compressors and limiters, and are found in some automated mixers.
VCA Group. Voltage Controlled Amplifier Group. A function of some live mixers that allows the engineer to control the level of a selected group of channels from one fader, without having to route those channels through a subgroup. Essentially, the VCA Group fader serves as a remote control, sending a voltage to a VCA on each of the channels being controlled.
VCF. Voltage Controlled Filter. A filter where the cutoff frequency and sometimes other parameters can be controlled using an external voltage. VCFs are common in analog synthesizers.
VCO. Voltage Controlled Oscillator. An oscillator where the frequency of the waveform can be controlled using an external voltage. In analog synthesizers, each additional volt raised the pitch by one octave (doubled the frequency). So each key in a keyboard controlling an analog synth would send out 1/12-volt more than the previous key in order to raise the pitch by a semitone.
vector synthesis. A type of synthesis developed by Sequential Circuits and later used by Korg, Yamaha, and other manufacturers. A vector synth has four simultaneous sound sources; the user can manually crossfade between the different sounds using a joystick or other control, or the synthesizer can be programmed to automatically crossfade through the sounds in a certain pattern. This creates sonic movement and sounds that can evolve over time.
velocity. How fast a player presses a key on a keyboard (not how hard, how fast)—literally, the time it takes for a key to go from the up position to the down position. Velocity is sent as part of a MIDI note on message and has a range of values from 0 to 127. Velocity is typically routed to control the volume of the note played by a key, but it can be used to control any other parameter, such as filter cutoff (higher velocity makes a note brighter), reverb amount, or any modulation destination that is supported by the receiving device.
velocity curve. A function in some keyboards that alters the instrument’s response to MIDI velocity messages to customize the “feel” of the keyboard (see Figure V.1). For example, scaling back velocity with a curve will make the player use a heavier touch in order to get the desired response from the keyboard.
Figure V.1. A velocity curve in a device can be used to customize the response or feel of the keyboard to match the player’s touch.
velocity microphone (a.k.a. pressure-gradient microphone). A microphone in which the output voltage is related to air particle velocity. Ribbon microphones are velocity or pressure-gradient microphones.
velocity response curve. See velocity curve.
velocity split. See velocity switching.
velocity switching. A function of some synths and samplers that can switch between two or more presets or samples in response to MIDI velocity. Play softly, and one sound is heard. Play hard, and a second sound is heard. See Table V.1.
Table V.1. Using MIDI Velocity to Switch between Samples in a Piano Patch
Velocity | Sample Played on Middle C |
|---|---|
0–20 | Very soft piano note sample |
21–40 | Soft piano note sample |
41–60 | Medium-soft piano note sample |
61–80 | Medium piano note sample |
81–100 | Loud piano note sample |
101–110 | Very loud piano note sample |
111–127 | Extremely loud piano note sample |
VESA. Video Electronics Standards Association. An organization that develops standards for video and multimedia systems in personal computers. Among the standards developed by VESA are various connectors, the SVGA video standard, the VESA Local Bus high-speed video bus, and more. www.vesa.org.
VGA. Video Graphics Array. A display system developed by IBM that has become standard in personal computers. VGA uses a 15-pin connector and offers up to 720×480 resolution and 262,144 colors.
vibrato. A musical effect used by instrumentalists and vocalists to add expression to a performance. Vibrato is characterized by cyclical, repeating variations in pitch, added manually during a performance or programmed into a synthesizer or sampler using an LFO to drive the pitch changes. See also tremolo.
video sync. See blackburst.
virtual. Existing only in computer software.
virtual analog synthesizer. A digital synthesizer that emulates or models an analog synthesizer. Physical modeling is used to re-create the characteristics of the components and circuits in an analog synth so that digital signals can be produced that sound as if they were generated and processed by real analog circuitry.
virtual instrument. A computer program that functions as a synthesizer or sampler, often as a plug-in within a DAW. Some virtual instruments attempt to “model” or emulate acoustic instruments or existing digital or analog hardware synthesizers; others strive to create entirely new sonic production and processing capabilities that do not have parallels in the hardware instrument world.
virtual track. 1. Tracks in a DAW that have been recorded into a song or session, but are not active or being played or used. 2. Tracks that have been recorded but cannot play because there are not sufficient system resources to play them. For example, a hardware digital recorder might be able to play up to 16 tracks simultaneously, but each of those tracks might have 16 “virtual” tracks that can be selected to play as alternate takes or different arrangements. 3. MIDI tracks that are driving synthesizers or samplers, but are not recorded to physical audio tracks.
VISE. Visual Installer Setup Environment. A program developed by MindVision that is designed to install other software products. Many software manufacturers use VISE installers to simplify the installation of their software. Just launch the VISE installer, and the software takes care of the rest, including decompressing files and placing all the software elements where required.
Vista Core Audio. Microsoft term for the audio protocols that are used in Windows Vista, including the Multimedia Device API, Windows Audio Session API, DeviceTopology API, and EndpointVolume API, which provide applications with access to a variety of capabilities when recording and playing back audio.
VITC. Vertical Interval Time Code. Time-code information encoded into the frames of a video signal instead of recorded to a linear audio track. The advantage of VITC over LTC is that the time code can be read while playback is stopped, which is not possible with LTC.
VO. See voiceover.
vocal booth. A small isolation room in a recording studio designed and treated for vocal recording, though other instruments are also often recorded in vocal booths. See also isolation booth.
vocoder. Voice Operated Encoder. An electronic instrument that uses the characteristics of a control signal to configure a number of filters that process the input signal. For example, the signal from a vocal microphone is used to drive filters that are processing a synth sound, effectively making the synthesizer “speak” or “sing.”
voice. 1. A note of polyphony in a synthesizer or sampler. 2. Another name for a preset or program.
voice coil. A coil of wire that is suspended in a magnetic field in a speaker. When signal flows through the coil, the assembly moves in the magnetic field, moving the speaker’s cone and creating sound waves.
voiceover. An announcer’s or commentator’s voice that is recorded over a background bed of music for an advertisement or other program material.
voice stealing. See dynamic allocation.
voicing. 1. Programming or creating synthesizer sounds. 2. Setting up and optimizing a studio monitor or live sound system. 3. Adjusting the sound of an acoustic piano to achieve a particular character.
volatile memory. RAM that loses its contents when the power is shut off.
volt. The unit of voltage. Named for Italian physicist Alessandro Volta.
voltage. A difference in electrical charge between two points.
voltage controlled amplifier. See VCA.
voltage controlled filter. See VCF.
voltage controlled oscillator. See VCO.
voltage regulator. A device that maintains a steady AC-line voltage despite fluctuations in the voltage coming from the wall socket. For example, in the United States, a voltage regulator might regulate wall voltage in the range of 80 to 130 volts to the standard 117 volts. Most voltage regulators quickly switch taps on transformers to maintain constant output voltage.
voltage sag (a.k.a. brownout). A temporary reduction in electrical power. In some cases, voltage sags are caused by the power company; in other cases, starting a high-current device will cause a brief sag in power. Voltage sags can wreak havoc on microprocessor-based devices.
voltage spike. See power spike.
volume. 1. The loudness of a signal, subject to the perception of the listener. 2. A computer hard drive or partition on a hard drive. 3. MIDI Continuous Controller #7, which is specified to control the volume level of a particular MIDI channel’s instrument.
VST. Virtual Studio Technology. A protocol developed by Steinberg and licensed to third-party developers and manufacturers for integrating software synths, samplers, effects, and processing plug-ins into a DAW. VST is a cross-platform standard, though it is not possible to use Windows VST plug-ins with Macintosh hosts and vice versa.
VSTi. See VST instrument.
VST instrument (a.k.a. VSTi). A virtual instrument that runs as a plug-in under the VST standard.
VST plug-in. A plug-in that conforms to the VST plug-in standard. See Figure V.2.
Figure V.2. The VST standard developed by Steinberg supports both processing and effects plug-ins and virtual instrument plug-ins. In this case, Spectrasonics’ Stylus RMX groove instrument is operating as a VST plug-in within Ableton Live software.
VST2. The second version of VST developed by Steinberg. VST2 added MIDI in and out ports to plug-ins, support for 24-bit/96-kHz sample rates, sample-accurate editing, and more.
VST3. The third version of VST developed by Steinberg. VST3 improved performance and added dynamic I/O (in which the plug-in’s I/O will automatically configure itself to the host channel’s I/O configuration), activating and deactivating output buses, audio inputs for VST3 instruments, resizable plug-in windows, and more.
VU meter. Volume Unit Meter. A mechanical metering device that displays average signal strength and is optimized to respond to loudness in the same manner the human ear does. Most VU meters don’t respond well to transients, so they may be accompanied by peak LEDs to indicate quick peaks.