MIDI has sprung from both music and computing, and uses terminology that can seem intimidating to the uninitiated. Here is a short glossary of some of the terms you'll encounter in this chapter.
MIDI File
A standard file format for storing recorded MIDI information. A MIDI file contains notes, timing, and instrument designations for up to 16 channels. The file contains information about each note, including the key, channel number duration, volume, and velocity (how quickly the key travels to its down position when struck).
Channels
The MIDI Specification provides for 16 channels of data—each channel addressing a separate logical synthesizer. Microsoft uses channels 1 through 10 for Extended synthesizers and uses channels 13 through 16 for Base-level synthesizers.
Sequencer
A computer program or electronic device designed for MIDI composition, which allows recording, playback, and editing of MIDI events. Most sequencers can import and export MIDI files.
Synthesizer
An electronic device that uses a Digital Signal Processor (DSP) or other type of chip to make music and sounds. A DSP creates and modifies waveforms and then sends them out through a sound generator and speakers. The quality and range of sounds made by a synthesizer depend on several factors: the number of individual waveforms (or instruments) the synthesizer chip can play simultaneously; the capabilities of its control software; and the memory size in the synthesizer circuitry.
Instrument
A specific sound that a synthesizer can reproduce. The patch number and sound quality of an instrument may vary from one synthesizer to another. For example, most synthesizers can play a piano sound, but it is likely to sound quite different and use a different patch number on different synthesizers.
Polyphony
This refers to the maximum number of notes that can be sustained by a synthesizer at once. For example, a four instrument synthesizer with six note polyphony can simultaneously play six notes distributed among four different sounds—perhaps producing a four note piano chord, a flute, and a violin.
Timbre
Pronounced “tamber.” This refers to the tone quality of a sound, which is determined by the combinations of frequencies from which it is formed. In more casual usage, it refers to the unique sound associated with a particular instrument. Bass, piano, or violin sounds are each examples of timbres.
Track
A MIDI file concept of separate, parallel groups of MIDI data, usually separated by channel. Format 0 MIDI files merge these tracks into one track; Format 1 MIDI files preserve the different tracks.
Patch Mapper
Software that reassigns an instrument patch number associated with a specific synthesizer to the corresponding standard patch number specified in the Microsoft standard MIDI patch assignments. The Windows with Multimedia MIDI Mapper maps instrument patches to any MIDI devices.
Channel Mapping
Channel mapping translates a MIDI channel number from a sending device to an appropriate channel for a receiving device. For example, drums authored on channel 16 can be mapped to channel 6 for a drum machine that only receives on channel 6.