MIDI stands for "Musical Instrument Digital Interface". It is a set of hardware (IN, OUT and THRU ports found on electronic keyboard instruments) and software specifications for allowing electronic musical instruments (and also computers) to communicate with each other.
The original MIDI specification was developed just over 10 years ago as a means for electronic keyboard players to play two or more keyboard instruments from just one keyboard. That way, Someone like Keith Emerson could "layer" his MOOG synthesizer from his Yamaha DX7 keyboard and have the two sounds going simultaneously to create a richer, beefier sound.
What does this have to do with computers ?
Shortly after the MIDI specification was created, dedicated hardware "Sequencers" were developed. These sequencers were like tape recorders, and allowed musicians to play a song on a keyboard and the MIDI output port would send the data directly to the sequencer to record the song. The musician would then press the "Play" button (just like a tape recorder) and the music would play back the performance exactly like the original. Beside that, it was being played "live" (by the sequencer), so sound quality reduction was no longer a problem as with traditional tape recorders.
About the same time, the Apple Macintosh and IBM PC were also evolving rapidly. Software developers came up with sequencing software for these computers. The software sequencers offered much greater capabilities than their hardware counterparts. Several years later, "Sound cards" became a standard on personal computers.
How do computers use MIDI files?
Sound cards typically employ two methods of sound generation. The main source are PCM type recordings (like *.WAV files on PC's). These are actually digital recordings, like the ones your CD player reads when playing a Compact Disk on your stereo system. While impressive to hear, these files use about 10 Megabytes/minute to produce stereo sound. These can use up quite a bit of hard drive real estate, in a very short period of time.
The second method a sound card uses to produce sound is on a built-in synthesizer. Music is played when a MIDI file triggers the sounds on the synthesizer. These MIDI files are small, and require very little storage space (a few kilobytes vs. a CD's 30 megabytes for a 3-minute song). As you can see, CD music files requires THOUSANDS of times more disc space for the same song.
While little space is required for the same song, most lower end sound cards employ a cheesy-sounding FM synthesizer. We've all heard those FM synthesizers when hearing tunes on those electronic holiday cards or when we are put on hold at some places. They sound kinda like cheap electronic bells.
What is "Wavetable" synthesis?
Higher end Sound cards (such as SoundBlaster AWE, Ensoniq Soundscape or Roland RAP-10) employ a different method of synthesis called "Wavetable" synthesis. The sound quality of most wavetable Sound cards is significantly better than the FM-based cards. Wavetable synthesizers use actual "digital samples" of real musical instruments, to generate music. These are real, hi-fidelity recordings of the actual instruments.
When a MIDI file is played through a high quality "Wavetable" sound card, the sound quality approaches that of an actual CD, but without the storage requirements. Remember, MIDI files take a fraction of the space required by audio (CD type) files.
What is General MIDI?
General MIDI (referred to as GM from here on out) was developed in the past 5 years and is the basis for "Wavetable" synthesis. GM is actually a set of 120 standard sounds, plus drum kit definitions. All "Wavetable" synthesizers and Sound cards use the GM soundset to assure compatibility between the manufacturers.
What hardware does my computer require to hear MIDI music?
All one needs to hear music is a sound card with speakers. As noted above, sound cards use two sources for sound generation. MIDI files use the synthesizer portion of a sound card. Music is played when a MIDI file triggers the sounds on the card. Most lower end sound cards employ a poor sounding ":FM" synthesizer.
We recommend a higher end sound card (such as SoundBlaster AWE ) which employ a different method of synthesis called "Wavetable" synthesis. When a MIDI file is played through a high quality "Wavetable" sound card, the sound quality approaches that of an actual CD. It does this without the extensive waiting time required to hear high quality sound over the internet. . (Remember, MIDI files take a fraction of the space required by WAV files.)
What if I don't own a sound card with "Wavetable" synthesis?
Software-based wavetable synthesis is now available free for those with lower-end soundcards. Microsoft has licensed the Sound Canvas soundset from Roland Corp. for their new Microsoft Synthesizer. Sound Canvas is the recognized reference standard for General MIDI and all wavetable soundcards. These software-based synthesizers usually require at least a Pentium-class PC to work properly, however.
Apple's version of QuickTime also uses the same General MIDI soundset from Roland Corp. This means that anyone with a basic sound card can now enjoy CD-quality Wavetable music just by installing one of these Synths on their PC or Mac. Users can click on the "Q" below to download the QuickTime Wavetable Synth.
The Roland Sound Canvas sound set provides the world's most highly acclaimed General MIDI wavetable sounds. This synthesizer is also compatible with the GS Format extension to General MIDI, allowing greater musical expression. Wavetable "daughter boards" are also available for most Sound cards. They sell for around $100.00 or more (depending on brand). These "daughter boards" plug right into your sound card, and basically override the cheapo "FM" synth once installed.