MIDI - Musical Instrument Digital Interface
by Ron Tongue

MIDI is an acronym that stands for Musical Instrument Digital Interface.

A basic MIDI setup generally consists of a computer, software, interface, and MIDI instrument. The computer and MIDI instrument (usually a keyboard instrument of some type) are connected together by a special type of MIDI cable. When a MIDI file is played on a computer, the music is played through the MIDI instrument. It is easy for someone new to MIDI to confuse a standard music recording such as a CD with an actual MIDI file.

NOTE!! The computer is not sending actual audio data to the MIDI instrument to be sounded. In actuality, the computer and MIDI instrument communicate by sending strings of numbers to each other very quickly.

These numbers tell the MIDI instrument which note to play, how loud to play it, how long to play it (when to release), and several other commands. The MIDI instrument responds to the MIDI messages coming from the computer by playing the instructed notes.

When you play a MIDI instrument into a computer with MIDI recording software, the software records the MIDI number commands, not the actual audio. Once the MIDI has been recorded into the computer, it is fully editable.

For example, if you played a wrong note you can easily find that note in your software and fix it with the click of a mouse!

OK, now for the longer definition.

As technology was advancing, many people became interested in making computers communicate. This desire for communication soon spread into the music technology world. It was in the year 1983 when MIDI (musical instrument digital interface) was first adopted by the MIDI manufacturers Association.

At first, the use of MIDI was a bit chaotic. Every company that manufactured MIDI instruments and equipment had their own codes and standards. Because of this, most MIDI gear was not able to communicate very well or at all with other manufacturers equipment. If they could communicate, it was often a nightmare because you would have to spend lots of time configuring your software so you could do things like select the proper instrument sounds or use the designated controller.

For example, if patch 15 was a flute on one keyboard, it may have been a trombone on another.

Eventually, MIDI developers put their heads together and came up with a solution. This solution was named "General MIDI" (GM). Once General MIDI was established, manufactures could design their instruments to follow the same minimum guidelines.

That way, patches (instruments sounds in a MIDI instrument), drums maps on the keyboard, number of channels, and controller data (volume = 7, pan = 10, sustain = 64, etc.) could all be standardized.

This now made it possible for someone to write a song on one machine using MIDI, bring it over to another machine and play it back using the same instrument sounds and musical expression.

To this day, General MIDI standards continue to be developed and improved.

To determine if your MIDI instrument is General MIDI compatible, look to see if somewhere on the instrument is the General MIDI logo.

If it is General MIDI compatible, which most are, you should have a sound bank with the following instrument sounds in the left column of this page.

So how exactly does MIDI work?

When you press a key on a MIDI keyboard, two signals are produced.

1.) The sounds you hear from your speakers.
2.) The MIDI data (numbers).

When a computer using MIDI software records a song you played into it using a MIDI keyboard, it is not recording the actual audio, but the numbers being sent down the MIDI cables. These numbers, when played back through a MIDI instrument tell the instrument information such as which note to play, how loud to play it, and how long to play it (note off).

When you play "middle c" on a MIDI keyboard, the following data is sent to the MIDI output of the keyboard:

Much more information than just note on, off and volume can be sent with MIDI. You can send other commands such as pan (fade left or right between stereo speakers), sustain (sustain pedal on a piano), patch change (change instrument sound), and just about any musical expression technique you can think of.

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.

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