Labels:text | screenshot | font OCR: General MIDI More and more modules and Keyboards are now General MIDI compatible. GM is supposed to make your life easier but what the hell is it all about? Written by Kevan R.Craft General MIDI-compatible equipment has been with us for two years now from 1991 1993, but most serious MIDI users consider it to be some form of distracting and largely 'consumer' addition. I must admit that I tended to lean towards that way of thinking until clients started to ask for GM MIDI Files for playing through their GM keyboards and modules for live gigs and performance purposes. Assigning appropirate sounds from a variety of non-GM modules takes time, and though a little judicious mapping can help here, a dedicated GM module makes life a lot easier. So, for the benefit of the uninitiated, what is General MIDI, or GM, as it is known in the industry? eneral MIDI Without getting too deep, General MIDI is another stage of standardisation which has been added to the existing MIDI protocol to enable MIDI manufacturers to build synthesizers and synth modules that exhibit a specified degree of compatability in certain areas. Specifically, General MIDI sets out strict rules for patch mapping, drum note mapping, multitimbrality and polyphony. In a nutshell, the aim is to allow a MIDI sequence recorded using one M module to be played back on any other GM module without the need to remap patches, move drum nates allocation or worry about running out of parts or polyphony. This doesn't mean that all GM synths have to sound exactly the same, but it does mean that, for example, a piano preset on one machine must be in the same patch location as a similar piano preset on any other GM machine. MIDI Compatibilty Normally, whenever you record a peice of music using a sequencer, you insert patch change commands at the start of the peice, and at any subsequent locations in the peice where a sound is required to change. That way, whenever you play back the sequence through the same instruments and modules, the correct sounds will automatically be called up with no intervention on your behalf. However, if you play the sequence back on a friend's MIDI system you may well find that all the sounds are completely wrong because the patches are not only completely different in sound but any that are also stored in different patch locations. In the case of programmable instruments, this kind of chaos is difficult to aviod because most users have their own system for storing their edited sounds. Furthermore, the factory presets that come with most MIDI instruments were not stored in introduction of GM. any particular order prior to the Another potential stumbling block is the drum and percussion part. Is your friend's set up with the drum part on the same MIDI channel and, if so, are the drum sounds mapped to the same notes? Roland have had their own more or less standard drum mapping system for some time now, but some other manufacturers have not been so well organised. Furthermore, you may have written the piece using drum sounds that don't have any closed equivalent on your friend's drum machine. Let's say you're lucky and you get all the sounds mapped out. There's still a good chance you' ll come unstuck when it comes to controller information; perhaps one of the modules doesn't respond to controller 7 (Master Volume), or perhaps the pitch bend ranges are set differently to those on your own system. The problem was that, although MIDI was a wonderful system for many applications there was too much that was still optional. General MIDI was devised to provide a solution for use in situations where a high degree of compatibilty was essential, for example when replaying pre-recorded MIDI song files. Now, with the introduction of General MIDI, musicians can play each other's GM song files and be confident that they will sound more or less the way they should, even though there are subtle subjective differences between one manufacture's GM machine and another. This has opened up the market for commercially available MIDI song files, and though these hold little attraction for the serious composer, they are very effective as live backings and may be used to gain recordin mixing and effects processing experience. Polyphony and Multitimbrality The problem with polyphony and multitimbrality is that you can never have enough of it! GM MIDI instruments provide the ability to play back 16 parts on 16 MIDI channels, but is a total polyphony of 24 notes sufficient to go round? if not, note robbing takes place and previously played notes start to drop out. The answer has to be that more would be nice, but we'll have to be grateful for what we get. What's more, where a synth uses two voices to make up a sound, the actual polyphony is further reduced. In theory, that means that a GM song file written for one GM macine could still come unstuck if played back using a different GM module claiming that number of voices and polyphony mena the same thing . Roland's Enhanced GS Format Much of the present GM format owes its existence to Roland's own protocols, so its hardly surprising that Roland have gone one step further and devised an enhanced version of General MIDI which they call GS. Realising that may users wouldn't be staisfied with 128 preset sounds, Roland have designed their GS machines to offer several alternative banks of sounds, Roland have designed their GS machines to offer several alternative banks of sounds, the basic GM set (Capital Tones) being the first bank (Bank 0). There are up to seven Variation Tones' based on each of the Capital Tones and these are arranged so as to have the same program change numbers as the tones from which they are derived. In other words, all the variation tones of a Piano Capital Tone will still be pianos, though they they will all be subtly different. Further banks are provided for sounds known as Sub-capital Tones, which are less obviously related to the Capital Tones. Editing Because General MIDI is based on the concept of the same sounds always being in the same place, it stands to reason that any attempt at editing the sounds will risk negating any advantages the system has. Some modules allow editing, though the patch name remains unchanged, while others retain the GM sounds as presets. Comercial MIDI Songs Files Over the past couple of years, companies have sprung up marketing GM song files covering all musical styles from pop to classical. These have many applications, from general interest to song analysis, but the area that has attracted the most interest is as an alternative to backing tapes for live performers. A huge advantage of MIDI song files over pre-recorded backing tapes is that the key can be changed at the touch of button, making life rather less difficult for the solo entertainer. The overall sound quality is generally better too; with pre-recorded tapes, you either have to play the original night after night and risk wearing it out cassette with the consequent loss of quality. or copy it to another GM SOUND SET 3: Piano 3 4: Honky-tonk Piano 5: El. Piano 1 6: E.Piano 2 7: Harsichord 8: Clavichord 9: Celesta 10: Glockenspiel 11: Music Box 12: Vibraphone 13: Marimba 14: Xylophone 15: Tubular-Bell 16: Santur 17: Organ 1 18: Organ 2 19: Organ 3 20: Church Org 1 21: Reed Organ 22: Accordian Fr 23: Harmonica 24: Bandeon 25: Nylon Guitar 26: Steel Guitar 27: Jazz Guitar 28: Clean Guitar 29: Muted Guitar 30: Overdrive Guitar 31: Distortion Guitar 32: Guitar Harmonics 33: Acoustic Bass 34: Fingered Bass 35: Picked Bass 36: Fretless Bass 37: Slap Bass 38: Slap Bass 2 39: Synth Bass 1 40: Synth Bass 2 41: Violin 42: Viola 43: Cello 44: Contrabass 45: Tremelo Strings 46: Pizzicato Strings 47: Harp 48: Timpani 49: Strings 50: Slow Strings 51: Syn Strings 52: Syn Strings 53: Choir Aahs 54: Voice Oohs 55: Syn Vox 56: Orch Hit 57: Trumpet 58: Trombone 59: Tuba 60: Muted Trumpet 61: French Horn 62: Brass 1 63: Synth Brass 1 64: Synth Brass 2 65: Soprano Sax 66: Alto Sax 67: Tenor Sax 68: Baritone Sax 69: Oboe 70: English Horn 71: Bassoon 72: Clarinet 73: Piccolo 74: Flute 75: Recorder 76: Pan Flute 77: Bottle Blow 78: Shakuhachi 79: Whistle 80: Ocarina 81: Square Wave 82: Saw Wave 83: Syn Calliope 84: Chiffer Lead 85: Charang 86: Solo Vox 87: 5th Saw Wave 88: Bass & Lead 89: Fantasia 90: Warm Pad 91: Plousynth 92: Space Voice 93: Bowed Glass 94: Metal Pad 95: Halo Pad 96: Sweep Pad 97: Ice Rain 98: Soundtrack 99: Crystal 100: Atmosphere 101: Brightness 102: Goblin 103: Echo drops 104: Star Theme 105: Sitar 106: Banjo 107: Shamisen 108: Koto 109: Kalimba 110: Bagpie 111: Fiddle 112: Shanai 113: Tinkle Bell 114: Agogo 115: Steel Drums 116: Wood Block 117: Taiko 118: M 118: Melo Tom 1 119: Synth Drum 120: Reverse Cymbal 121: Gt Fret Noise 122: Breath Noise 123: Sea Shore 124: Bird 125: Telephone 126: Helicopter 127: Applause 128: Gunshot Some Current GM Synths Roland SC55, SC155, , SC7 and JW50 Boss DS660 Dr Synth Dream GMX1 Kawai GMega Korg 03R/W Yamaha TG100 General MIDI Requirements In 1991, General MIDI was ratified with the aim of defining a minimum set MIDI capabilites to which all GM MIDI devices must adhere. The main points are as follows :- * A GM instrument must support all 16 MIDI channels simultaneously to provide 16-part multitimbrality. * Percussion parts must be on Channel 10, a minimum set of 47 standard sound types, including the most common drum and latin percussion sounds, must be provided and these must all be mapped in accordance with the GM standard. This mapping owes a lot to Roland's original mapping system. * Gm instruments must be capable of 24-note polyphony and notes must be allocated dynamically. However, the specification allows eight notes to be reserved for percussion, leaving 16 for the other instruments. * All 128 preset sounds are defined as to their type and patch location. Though there are some variation i in sound between one module and another, the instrument type (and even playing style in the case of basses, for example) for each patch location is quite rigidly defined, right down to the dog barks and gun shots in the special effects section. Some of the sounds, such as pads, are a little more flexinble but they must still be of a roughly similar tone and style. * All GM instruments must respond to the same set of MIDI Controllers. The MIDI Controller implimentation includes the abilty to change master tuning and Pitch Bend wheel range via MIDI, Reset All Controllers, (which resets all MIDI Controllers to their default values), and All Notes OFF. All GM machines must also respond to Pitch Bend and Aftertouch. Kevan R. Craft MIDICraft Compositions and Arrangements 12 Mount Road Halton Runcorn Cheshire. WA7 2BH. England. U.K. Tel: +44 0928 563762
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