General MIDI
What is General MIDI?
M.I.D.I. is "Musical Instrument Digital Interface". General MIDI (GM) is a music industry specification for electronic music devices that respond to M.I.D.I. (MIDI) messages. GM was developed 1991 by the MIDI Manufacturers Association (MMA) and the Japan MIDI Standards Committee (JMSC).
Before General MIDI
Before General MIDI, MIDI devices made by Korg, Yamaha, Ensoniq, Roland and other manufacturers had no 'standard' layout. Therefore a MIDI File created with the instrument layout on a Roland device might not playback as intended through a Yamaha device. Piano sounds on a Roland device might reproduce a bass guitar on a Yamaha or other manufacturer's device. The drum track created on a Korg device may reproduce a brass ensemble on a Ensoniq device. This state of events made it difficult for musicians to collaborate on a project and made it impossible for commercial MIDI File producers like Hit Trax to format MIDI Files for universal application and use.
Primary Use of General MIDI
The primary use of General MIDI is to create and play back backing tracks commonly known as MIDI Files. A MIDI keyboard is connected to a computer or other device by a MIDI or USB cable. The computer or an app record and playback the 'MIDI messages' transmitted by the MIDI keyboard when notes are pressed. Some MIDI keyboards include a recorder and sounds and operate independently from a computer.
General MIDI Keyboard - MIDI Messages
MIDI Messages can be something simple like pressing middle 'C' on a General MIDI keyboard. The press sends the note (note on), the pressure exerted on the note (velocity), the length of time the note is held (note length) and when the note is released (note off) to a MIDI software program or app. The resulting sound is reproduced through a MIDI File player or sound samples. Popular software includes Logic Pro X (Apple), Cubase (Steinberg), Sonar (Roland) and Pro Tools.
General MIDI Instruments
General MIDI has 128 instruments. Each instrument has an identifying program number between 0 and 127. For example, stage piano has a program ID of #0. An electric bass has a program ID of #33. A steel string acoustic guitar has a program ID of #26. A full list of General MIDI instruments and their ID numbers can be downloaded in the related links section at the end of this article.
General MIDI Sounds
General MIDI categorises the 128 instruments into 16 'instrument groups' . Group 1 is piano's. Here, we find a normal piano, honky-tonk piano, some electric piano's and other piano variations. Other groups and their variations are Chromatic Percussion, Organ, Guitar, Bass, Strings, Ensemble, Brass, Reed, Pipe, Synth Lead, Synth Pad, Synth Effects, Ethnic, Percussive and Sound Effects.
General MIDI Drums
General MIDI includes 7 preset drum kits. Standard Drums, Room Drums, Power Drums, Electronic Drums, TR808 Drums, Jazz Drums and Brush Drums.
MIDI Channels
General MIDI has 16 available channels to input MIDI Messages with one instrument from any instrument group assigned to each channel. There are some exceptions. Bass guitar is always allocated to channel 2, melody guide to channel 4, melody harmony parts to channel 5 and drums are exclusive to channel 10. Piano generally occupies channel 1 but apart from the exceptions, any instrument can occupy a MIDI channel. It is not necessary to use all 16 MIDI channels. Instruments are activated by inserting the instrument ID in the designated channel. Controllers including volume, pan, reverb amount and other variables are inserted into the channel by inputting the controller and its value (amount ranging from 0-127). Now, the channel is ready to receive, record and playback MIDI messages.
General MIDI Explained
Imagine a TV. This TV has 16 channels and each channel is dedicated to an 'instrument group'. Channel 1 is a piano sound. Channel 2 is a bass guitar. Channel 3 is another instrument and so on. All 16 channels are each dedicated to an 'instrument group'. We flick through each channel and can only hear one channel at a time.
Now imagine hearing all 16 channels at once! Well, that's exactly what happens when 1 or more channels of MIDI messages are recorded and played back. Therefore, a musician can create a song (MIDI File) instrument by instrument and track by track. But most importantly, the MIDI File will reproduce exactly across any General MIDI device created by any MIDI instrument manufacturer. Cool, huh?
General MIDI and Hit Trax
Some time in 1991, when Hit Trax and I were very young, a friend of mine came by for a visit. Mal had just returned from Japan touring with a band and had in his hands Roland's very first General MIDI device, the SOUND CANVAS SC55. This 1/2 rack space module came with an intimidating user manual written in Japanese.
The SC55 was plonked on my desk with a "return it whenever you want" gift from Mal. So, with no Internet, no email, no YouTube and no search engines (it was 1991 ...) I typed and faxed a letter to Roland's headquarters in Japan requesting an English manual. Soon enough, a bare bones English manual arrived by fax, translated directly and literally from Japanese. Those manuals were intimidating to say the least.
MIDI Files Evolve for Universal Use
The first positive I noticed was the ease in selecting and setting up instruments. Back then I was using an Atari computer running "Notator". Using a General MIDI template file, I imported the first of the 232 MIDI Files I'd created and one by one, reset them to General MIDI format. Thus, was born the first Hit Trax catalogue. Soon enough, other manufacturers got onboard the General MIDI train. Roland was really the world leader in General MIDI followed by several European manufacturers including M-Live, Charlie Lab and Ketron among many others.
General MIDI and Performers
Baby boomer musicians and pub goers will remember the explosion of solo artists, duo's and trios using backing tracks in the early 90's. That's where it all started folks. Venues with limited space booked live (semi-live...) entertainment. The demand for these smaller 'sequenced bands" cannot be understated. Bands gigging one or two nights a week created offshoot smaller bands to gig other nights using MIDI File backing tracks. The demand for 'sequenced' bands was unprecedented. General MIDI made this performing evolution possible.
General MIDI In The Modern Era
General MIDI is just as important today. MIDI Files remain the primary source of backing tracks for singers musicians and bands. Performers on TV talent shows like The Voice and X Factor use backing tracks derived from MIDI Files. Performers using MP3 backing tracks should know their song files were most likely a 45kb MIDI File before being monsterised into a 6mb Mp3 !
General MIDI Beyond Music
I'll leave you with this. General MIDI has uses other than music. Do you know a General MIDI File can control a space mission from launch to touch down, or operate the electrics in your home, or control traffic lights and airport control towers.
Article by John Ialuna, founder and director of Hit Trax.
RELATED LINKS
MIDI Files
What is a MIDI File?
MIDI
What is a M.I.D.I.?
General MIDI Instrument List
View General MIDI group and instrument list