Note
to readers: In subsequent columns I will be discussing more advanced
topics, but this introduction is intended for MIDI beginners. Also, this column
is a little longer than those which will follow.You may have heard that MIDI is an acronym for Musical Instrument Digital Interface. MIDI is basically a standard way for various electronic musical instruments to interact with each other. For example, if you have a MIDI-capable keyboard, you can connect it to a drum machine and trigger the drum sounds using the keyboard. You could even connect up two or more keyboards and play them all simultaneously.
Since you are reading this on your computer, I assume you are most interested in using MIDI on your PC. The reason you are able to hear MIDI tunes through your computer is that you have a MIDI-capable sound card inside the machine. Most sound cards these days are capable of playing MIDI files, but some do a much better job than others (more on that later).
There are basically two types of sound files which can be played on your computer. In addition to MIDI there is also digital audio. Digital audio files for the PC are called wave files and usually end with the file extension .wav. Digital audio files for the Macintosh end with .aif or .aiff and those for Unix machines end with .au. Recording digital audio is very much like recording with a tape recorder--you use a microphone to capture speech or music. Therefore, vocals, musical instruments, sound effects or any type of sound can be captured on digital audio, while MIDI can be used only for music which can be played back on a synthesizer or computer sound card.
If digital audio is so much more versatile, then why use MIDI at all? There are several reasons. One very big reason, especially applicable to sending files over the internet, is file size. Digital audio files can be huge; even a very short song could take up tens of megabytes of storage space. If you have ever downloaded audio files from Web pages, then you know what I am talking about. You sit at your computer for several minutes, waiting for the file to be transferred. When it finally arrives, it may last only two or three seconds. There are several ways to compress audio files to make them smaller (such as mpeg audio), but they are still relatively large when compared to MIDI files.
MIDI files transferred over the internet work just the opposite of digital audio--a tune which takes just a few seconds to download will play for several minutes.
Another big advantage of MIDI is that it can be edited. MIDI is recorded using a software program called a sequencer (there are also hardware devices called sequencers which do the same thing). Using a sequencer is very much like using a word processor--you can cut, copy, paste and delete musical notes in much the same way as you would edit words. Measures can be moved around or copied to make the song longer or shorter.
A MIDI file (or "sequence") is created by entering notes with a MIDI device. Usually this is a keyboard, but there are adapters which allow MIDI notes to be entered with a guitar or other instrument.
Unlike digital audio files, MIDI files do not contain actual recorded music. Instead, the music sequence is recorded as a series of numbers which explain how the music is to be played back. For example, to reproduce the sound of a piano playing a C note, the MIDI sequence contains digital information which says " this is a piano sound." Another number says "a note has been played," other numbers convey information such as "the note is middle C," "the key was struck very softly," "the sostenuto pedal was pressed," "the note has now stopped," etc.
An easy, if somewhat oversimplified way to explain a MIDI file is to compare it to an old-fashioned player piano roll. Player pianos use rolls of paper with perforations which correspond to the notes to be played. A player piano roll contains the musical information needed to play back a particular song, but it is useless without a player piano.
Likewise, MIDI sequences must be played back on another MIDI device. This is the major disadvantage MIDI has in relation to digital audio. A sequence recorded on a Roland synthesizer will not sound quite the same when played back on a Yamaha. The biggest differences are encountered when playing sequences on a home computer.
Sound cards use one of two methods to play back MIDI notes--wavetable sampling or FM synthesis. Cheaper sound cards and most older sound cards use FM synthesis to reproduce the sounds of the various instruments used in the MIDI sequence. That is, they approximate the sounds by using a built-in synthesizer. The results are very "synthetic" indeed.
Wavetable sound cards, on the other hand, contain digitally-recorded pieces, or "samples" of real instruments. The manufacturer of the sound card actually records a real piano to serve as the piano sound. Since most sound cards can reproduce the sounds of at least 128 different instruments, the sampling process is very critical and time-consuming.
The bottom line is that MIDI sequences sound much better on high-end, wavetable cards. If you are buying a new sound card, make sure it is a wavetable one. In subsequent columns I will discuss the various brands of sound cards and software programs.