One great aspect to MIDI is the ability to combine instrument sounds together as you would with a traditional instrument ensemble. The biggest advantage is that you don't need several musicians to form your ensemble, just you!
In order to use MIDI effectively for this purpose, you need to understand the difference between channels, tracks, and polyphony.
MIDI Channels
To start with, the General MIDI standard is 16 channels. This partially came about because a standard 5 pin MIDI cable is only capable of transmitting 16 channels of data.
Most any MIDI keyboard purchased today is capable of playing 16 channels of audio simultaneously. That means you can compose or arrange a piece that can use up to 16 instruments at the same time.
NOTE!!MIDI "channels" are the number of channels or streams of data that can be sent down one set of MIDI cables to one MIDI instrument.
MIDI Tracks
MIDI tracks are different from MIDI channels.
The tracks are established within the MIDI software on your computer you are using. Most MIDI recording software advertises that it can have 128, 265, or unlimited MIDI tracks.
It is important not to confuse the tracks with channels.
NOTE!!Even though you may be able to have 128 tracks, does not necessarily mean you can play back more than 16 channels of MIDI data with one MIDI instrument.
Another thing that can make this more confusing is that track one is not necessarily channel one. You have to specify with MIDI channels you are using per track. Refer to your software documentation on how to do this.
It is also possible to have more than one track using the same MIDI channel. For example, say you want to record a piano part for your composition. You may decide to have the right hand part on one track and the left hand on another.
Track 3 = Left Hand
Track 4 = Right Hand
Both Tracks assigned to the same MIDI channel (Channel 3).
Another example might be when you are recording drums. You may use multiple MIDI tracks all routed to the same MIDI channel.
Track 1 = Kick
Track 2 = Snare
Track 3 = Hi-Hat
Track 4 = Rack Tom
Track 5 = Floor Tom
All tracks are assgned to the same MIDI channel (Channel 10).
Why would you split up a drum kit into multiple tracks?
This makes it easier when making changes after the track is recorded. For example, it's much easier to mix the drums together like if the kick drum is too loud. You can easily change the velocity (volume) of just that track.
Polyphony
The word polyphony has been around for hundreds of years. Its first reference to music probably came about during the Middle Ages when chant music was popular. Although, its definition is slightly different when used in context with MIDI.
Basically, polyphony is the amount of notes that can be played or sounded at the same time.
Most low-end MIDI keyboards are capable of playing 32 notes at once (32 note polyphony). In other words, if you were to press and hold 32 keys on the keyboard, you will hear all 32. But if you press 33, one of them won't sound.
Most high-end MIDI keyboards are capable of playing 128 notes at once (128 note polyphony).
But I can't play 32 notes at the same time! Actually...
You may quickly run out of available notes when using several tracks and channels. It adds up in a hurry.
In Fact...
Even a one track piano piece can easily eat up all 128 notes of polyphony. You have to remember that the notes held by the sustain pedal are also counted. So, if your next project is a piano concerto with symphony orchestra, you may need a more advanced setup.
All in all, the number of polyphony an instrument can handle is very important when deciding which instrument to buy. What happens when you run out of polyphony? The notes that were played first start dropping out to make room for the new ones. This can totally ruin a creative idea when your instrument is not capably of playing your hard worked material.
Keep this information on channels, tracks, and polyphony fresh in your mind as you read this next section on the MIDI interface. Knowing how many channels you may need and available polyphony will dictate which interface you'll need.
