Understanding MIDI Signal Flow

In order to help you understand what this MIDI in/out nonsense is all about, you really need to understand signal flow. When you truly understand signal flow, you will be able to make sense of all your ins and outs no matter how complicated things get. You determine signal flow by defining the path that a signal needs to travel to get from point A to point B. For example, let’s analyze what happens as a key is struck on a piano. A finger strikes a piano key, and the key moves a hammer, which in turn strikes multiple strings, which creates a pitch. The pitch is then amplified by a soundboard in the piano and heard by some guy sitting across the room. Even though this may seem detailed to some, it’s actually a fairly simple description of what really happens when a key is pressed on a piano.

Now let’s create a simple signal-flow map starting with striking a key on a MIDI keyboard. Your finger strikes a key on the MIDI keyboard, then the signal travels out of the MIDI Out on the keyboard and in to the MIDI In on the computer through a USB or MIDI cable. Now, once the signal is in the computer, the signal must flow out to a synth or sampler’s (MIDI sound source) MIDI In. Once the signal has reached the MIDI sound source, it is translated into an audio signal, and the audio signal then must go out of the MIDI sound source and through some sort of speaker so that you can hear the key your finger just struck. Whew! That was a lot of ins and outs (and that was a shortened version of what really happens to the signal)! If you can follow this example and always ask yourself where the signal needs to go in detail, you should be able to figure out when you’ll need to use an in or out and which in or out you need.