In this article, I will take an overview of the various first generation devices Roland released bearing its "Sound Canvas" branding and GS standard and their importance to PC gaming. I characterize a "first generation Roland GS device" as any device with the features of an SC-55 but not the full features of an SC-55mkII.
In 1991, Roland released its SC-55 MIDI Sound Generator, its first GS product. This machine supported 16 MIDI channels (percussion on channel 10), 128 capital tones, 69 variation tones and 8 percussion/drum sets. It could support up to 24 voice polyphony at one time (each instrument using 1-2 voices or partials). It also had an effects processor with chorus and reverb which games (Ultima VIII : Pagan) have used. It has a battery to remember the user's settings This is a standard CR2032 coin cell in a holder and should be replaced or removed when you purchase a unit.
Its backlit LCD screen will show which tone is being played by which part, and games can also control the text at the top of the display (Lands of Lore). All first generation devices also supported 128 MT-32 tones and a MT-32 + CM-32L percussion set (63 sounds). The total Sound Canvas patch set is 3MB in size, 1MB of which is probably dedicated to the MT-32 tones
The SC-55 has two MIDI IN ports, one MIDI OUT and one MIDI THRU port. It has two RCA input jacks and two RCA output jacks and a headphone mini-jack. It also comes with a hand held remote but no software. It has 18 front panel buttons. From here you can mute all sound output from the module, which is very useful if you are sending the input from an MT-32 or CM-32L through it. You can set the MT-32 emulation mode by pressing the instrument left button as you turn the power on and pressing All. You can set the GS mode by pressing the instrument right button and pressing All. You can do a full factory reset by holding both instrument buttons and pressing all.
The earliest Roland SC-55s simply have a "GS STANDARD" logo on the bottom of the front panel, while slightly later SC-55s have a "GS" logo. Modules with the GS logo may still be
Between these Roland SC-55s and the later devices, there were two changes in the instrument map. Early modules have at Program Change #121 Fl. Key Click. There is no Breath Noise tone. Later modules in the series would put Breath Noise as the default tone on PC#121 and put Fl. Key Click as a variation tone. Breath Noise is the canonical General MIDI tone for PC#121. Early modules lack a sine wave variation tone at PC#81. These changes can be seen in all General MIDI/GS units and even some simply "GS" branded units. GS branded SC-55s with a Control ROM version of 1.10 will have the old instrument table, while units with a 1.20 or 1.21 Control ROM will have the new instruments.
If you want to find the version number of your unit, put the SC-55 in standby mode and press both Instrument buttons followed by both MIDI CH buttons. The information will flash on the LCD panel.
A hypothesis has circulated that certain PC game composers may have used an early "GS STANDARD" to compose their music. Examples included Descent and Descent 2, DOOM, DOOM II or Duke Nukem 3D. However, the composer for DOOM I & II and Duke Nukem, Robert Prince, has stated that he did not use an early SC-55. Moreover, at least six composers contributed to Descent and Descent 2. There is little likelihood of more than one or two of them using an early module. I would suggest that this hypothesis is a myth that has been debunked.
Next, Roland released the SCC-1 IBM PC sound card. This card contained the synthesis portion of the SC-55 with a cut-down Roland MPU-401 interface. No battery, no display. Nonetheless, if a game had an install option for the Roland SCC-1, the exact same functionality will be present though a Roland MPU-401 card/breakout box connected to an SC-55 via MIDI OUT. The SCC-1 has two RCA output jacks, one headphone mini-jack, one MIDI OUT and one MIDI IN mini-DINs. They need adapters to full DINs. Pinouts can be found here : http://nerdlypleasures.blogspot.com/2010/03/tutorial-how-to-get-roland-mt-32.html
Soon after, Roland released the GS compatible devices in its "computer module series", the CM-300 and CM-500. The CM-300 has the exact same capabilities as the SC-55 except no LCD panel or buttons and fewer ports. The CM-500 is a CM-300 combined with an CM-32L. Both CM modules lack a battery. Both have one MIDI IN, MIDI OUT and MIDI THRU ports. They also have two auidio output 1/4" jacks, one stereo headphone 1/4" jack. The CM-300 has two audio input 1/4" jacks, intended for an MT-32 or CM-32L's input. The CM-500 has a four-position mode switch instead. The CM-500 is a true Roland LA Synthesis device, but its vibrato has been criticized as noticeably harsher than the MT-32, MT-100, CM-32L, CM-64 and LAPC-I. The SCC-1, CM-300 and CM-500 also support the first 64 tones ("built-in") of the CM-64 module, although the instrument sample quality is superior on the true CM-64.
By no later than March of 1992, Roland added official support for the General MIDI standard to the SC-55, CM-300 and CM-500. These modules are identified with the General MIDI logo being next to the GS logo. Unlike the SC-55mkII, the SC-55 cannot initialize GM mode via the front panel. However, it can turn the GS features off by pressing the part buttons simultaneously, using the all and mute buttons to get to the Rx GS Reset item and pressing the instrument left button to turn it off (and the right button to turn it on).
What does the addition of General MIDI support mean in practice?
General MIDI is a derived subset of the GS standard. In other words, GS is General MIDI with some extra features. In a pre-General MIDI module, if a GS reset or a GM reset was sent to the module, it would have the identical effect, the module would be reset. In a General MIDI module, a GS reset would turn on GS features (variation tone support and NRPN) if the device was in GM mode. You would think that a GM reset would turn off those GS features. However, this is not the case unless the setting of Rx GS Reset is turned off. In that case, games that use variation tones will not be used (Might and Magic IV-V).
In the beginning of 1992, Roland released the SC-155. This device added sliders to control various settings of the synthesizer and otherwise looks like an SC-55. This is the first device that officially supported the General MIDI standard on its release, as would all Roland products released thereafter.
Later in 1992, Roland released the JV-30 Keyboard. This was a music synthesizer keyboard with 61 keys and could save the user's modifications to individual tones. It appears to contain the extra tones found in the SC-55mkII. However, unlike the mkII it does support capital tone fallback.
What is capital tone feedback and why is it important?
Each of the 128 Capital Tones can support 127 Variation Tones in the GS standard, even though the upper limit never came close to being never reached. If a composer used variation tone #5 of capital tone #1 (Grand Piano), in his MIDI synthesizer for a certain piece of music, it would not play if a listener played back the song on another device that did not contain variation tone #5. In the early first generation GS devices, if the specified variation tone did not exist in the module, then the module would fallback and play the capital tone instead. Since variation tones are supposed to be similar to the capital tone, some semblance of the sound the composer intended would be played. Beginning with the SC55mkII, however, no sound will be heard if the song selects an invalid variation tone. This can be manifested when programmers got lazy and relied on this feature instead of sending proper Program Change and Bank Select messages (Space Quest V : The Next Mutation).
Finally, Roland released an update to the SCC-1. The board itself is labeled the SCC-1A. It has the extra sounds of the JV-30 Keyboard but does not support capital tone fallback. This was a feature patented by Yamaha apparently.
Also during 1992, Roland released the General MIDI only SC-7. This cut down module does not support the GS standard, so no variation tones. However, it does support a Serial MIDI interface (no longer useless for DOS games because of SoftMPU) and 28-voice polyphony. It also supports six out of the nine drumsets, reverb and chorus found in a true Sound Canvas. The SC-55mkII would incorporate the increased polyphony of the SC-7 and the sounds of the SCC-1A.