History Of PC Game Music
Flashback to the early to mid-90s: DOS was still going strong, Windows 95 was brand new, the first-person-shooter was on the rise, 3D graphics looked like jagged, pixelated, and unstable mishapen blocky objects (yet they still impressed us and blew us away). Games like Wolfenstein 3D, Doom, Descent, Duke Nukem 3D, and Quake were the top-of-the-line best selling high-quality games advertized on store shelves. The technology for digital music in a computer game was still very young. There wasn't much storage space for a lot of high quality game content on floppy disks, hard disks, or CD-ROMs (the DVD-ROM wasn't yet available). In order to conserve disk space for the consumer and to fit as much content as possible into a game, developers generally chose not to use digital audio formats for game soundtracks. In addition to this, the hardware did not yet exist for efficient or adequate playback of high quality digital audio while running a whole game engine with a decent framerate at the same time.
If a game did have digital music it was probably in the form of CD audio tracks on the game's CD-ROM disc. This gave perfect audio clarity to a game's soundtrack but lacked any real control other than "play track", "skip track", and "stop track". There was no looping capability which led to breaking the immersive game experience when a song would suddenly stop playing in the middle of an intense battle. The CD-ROM drive had to be set up correctly along with the user's sound card software/hardware in order for it to be heard at all. Also, some games were so large that they had to supply two CDs: one with the game data and the other with the game soundtrack. Some people didn't like juggling around so many CDs. So while this method had perfect audio quality despite the sound hardware your computer might have, it wasn't the ideal choice for a picture perfect gaming experience.
Another popular form of digital game music at the time was the MOD file format (short for "MODule"). MODs were unique in that they had all the wavetable instruments stored in the file along with the musical notation and effect information (like volume/panning changes). This offered the composer a little more freedom and creative control over how the soundtrack would react to what the player was doing at any given time. The best example of this is the game Unreal, where if an enemy noticed you and started to chase and attack you the music would seamlessly transition into an upbeat battle theme. After the battle was over, the music would transition back into the previous more relaxed exploration theme. All this was done with realistic instruments. However, the instruments used inside a MOD file, though being chosen specifically by the composers themselves, were often of low quality for the purpose of (you guessed it) conserving disk space.
By far the most versatile and oldest game soundtrack medium was the MIDI file (Musical Instrument Digital Interface). MIDI files were tiny in file size due to the fact that they don't really contain any audio information at all. For example, a 2-hour long MIDI file could have a file size of only around 900KB! MIDI files only contain the musical notation and effect information which is sent to an outside destination that interprets it and outputs it all into the audible form we know as music. MIDI also had the ability to set loop points. It also had the capacity to make real-time dynamic changes to musical information such as: the current instrument being played, the volume/panning/velocity settings of any instrument, and even the ability to alter custom effect information like reverb, chorus, delay, or distortion depending on the hardware in use and if the game soundtrack supported them. The best example of games that used this technology extensively were the early games made by LucasArts. With their custom proprietary music engine called 'iMuse', they were able to make such dynamic changes during gameplay depending on what the player was doing and what events were triggered at any given time. The most impressive LucasArts title to take full advantage of this technology was Monkey Island 2: LeChuck's Revenge.
The term "FM Synth" is shorthand for 'Frequency Modulation Synthesizer'. Rather than relying on expensive external MIDI hardware, consumers could buy relatively cheaper 8-bit ISA cards with FM synth capability. FM Synth became the most popular game music standard because of its price in comparison to external hardware, versatility, and distinct memorable tone. Many users even now prefer the sound of an FM synth music card as opposed to the dazzling digital audio possibilities of today. Nearly every single PC game released for DOS that has a MIDI (or equivalent) soundtrack supports an FM synth card of some variant.
The best of the most popular cards that used this form of MIDI representation were Creative Labs' Sound Blasters and AdLib's Music Synthesizer cards. While AdLib founded and perfected widespread use of FM synth on the PC with each new model release of the AdLib card right up to the AdLib Gold (which sported an impressive stereo OPL3 FM chip!), Creative's Sound Blaster evened out the odds with their support for both AdLib-compatible FM synth music and digital sound output. And while AdLib did eventually support digital sound with the AdLib Gold card, it was sadly too late a move for the company as it wasn't Sound Blaster-compatible. Since the Sound Blaster was the more popular and much cheaper choice, not as much support was given to the Gold by game developers which hurt its sales. The Gold was the last card AdLib would produce and filed for bankruptcy in the same year of its release. Meanwhile, the Sound Blaster was going strong and long established as the de-facto standard in PC-gaming audio and is to this day. The latest model on the market as of this writing is the Sound Blaster X-Fi.
Sadly, the Sound Blaster and all other available sound cards have long abandoned support for FM synth. However, FM synth is now successfully emulated with remarkable results with a plugin called AdPlug (for use with media players like WinAmp for Windows and XMMS for Linux) and with built-in music options for emulation programs of old PC games and hardware. Such free and open source programs dedicated to playability of old DOS games as ScummVM and DOSBox both support integrated OPL emulators among many others.
As people grew tired of FM synth, some affordable higher quality MIDI cards became available. Realistic-sounding instruments were now possible with the increasingly popular Wavetable synthesis concept. Wavetable synthesis used digital PCM samples of live recordings of synthesized or real instruments to play MIDI data. Wavetable MIDI is now the standard in modern sound cards. Even Roland created internal cards of their external MIDI hardware like the LAPC-I (MT-32 equivalent) and the SCC-1 (SC-55 equivalent). One of Creative's best Sound Blaster cards ever released was the Sound Blaster AWE32 which supported the highest quality digital audio of the time along with the Adlib Gold's stereo OPL3 FM chip (in early models), compatibility for external MIDI hardware, AND a wavetable soundset built right onto the card. Not only that, it also had expansion slots so you could put extra memory on the card for even more wavetable voices! What a loaded card! The AWE32, however, was created for competition to the immensely popular Gravis Ultrasound card (which has a cult following even to this day). Many DOS games of the era supported the SC-55, GUS, and AWE32 as the best possible ways to experience their soundtracks. But despite this, neither the GUS nor the AWE32 were as supported as the SC-55.
Roland MIDI Synthesizers
Roland had monopolized its products among the computer gaming community as the highest standard of possible game music quality one could experience. Scaling back a few years, they began their conquest of the gaming market in the late 80s with the MT-32 synthesizer. This unique and powerful little black box may seem like a weak contender at first glance, but its ability to program (via system exclusive MIDI data) custom timbres to make your own instruments with its unique linear algorithmic approach to synthesizing waveforms and combining them with PCM samples made it a powerful tool for composers. A leading game company at the time named Sierra On-line first took advantage of this opportunity and made a deal with Roland to help sell its synthesizer by supporting it in their games. King's Quest IV was the first game to support the MT-32 and its soundtrack was scored by film composer William Goldstein. Once other developers saw what was possible and how much better it was over an FM Synth card they followed Sierra's lead and supported the device in their own games. The MT-32 became the standard for computer game music for the next few years.
Because of the way the MT-32 offered custom instrument programming it was the only synthesizer that MIDI files written for it could be played on. And because it was so expensive not everybody could afford it. This contributed to the creation of the General MIDI standard in 1991. General MIDI was a set MIDI format with a list of 128 unchangeable instruments over 16 channels (the MT-32 only had 9 channels) so that, unlike the MT-32's ability to program custom instruments, MIDI files would all have the same list of instruments so that no matter what hardware you used to play them back it would sound the same on all of them (more or less).
The Sound Canvas
In the same year Roland built on the GM standard with the release of the first Sound Canvas (the SC-55) and created GS (General Standard or General Sound). GS expanded the original 128-instrument GM standard via variation banks to over 300 instruments (as well as support for the default MT-32 standard, though without its re-programmability) and added a few proprietery MIDI controllers like Reverb and Chorus both of which could be triggered via MIDI data. This was highly successful because not only did the SC-55 natively support the GM standard, but to increase compatibility composers could compose within the 128-instrument GM limitations but still use the proprietery reverb and chorus controllers of GS. Not only did this make it easier to compose and ensure compatibility across whatever hardware the consumer might have, but it also gave an incentive for users to buy an SC-55 anyway for its enhanced effects that were unavailable with other hardware right out of the box! From that point on games with MIDI soundtracks almost universally supported the Sound Canvas as the best way to experience them. So much so that Roland created a software wavetable MIDI synthesizer based on the SC-55 for Windows XP called "Microsoft GS Wavetable", though the quality is no where near as good as a real SC-55 and it's missing some MIDI controllers like reverb and chorus among others.
Now years later, while many may consider the quality of the SC-55 to be sub-par (especially for a game music pack), SC-55's are now fairly cheap to acquire on eBay and the like. The idea of playing a game the way it was always meant to be heard appeals greatly to many nostalgic gamers out there. To experience a game the way the original composers meant their soundtracks to be heard is truly an honour. Especially when people like me couldn't afford a Sound Canvas or an MT-32 back in the day. Since I now have the pleasure of owning one I feel it's my joy and responsibility to share this ability with others. It's all the more relevant now that more and more games are getting modern source ports of the original engines. EDuke32, GLRott, ZDoom, Dxx-Reborn (Descent), and plenty more source ports of your favourite games all support digital music packs to replace their MIDI equivalents. It's a perfect time to play your games like you wish you could have back in 1996!
Special thanks to Salient, Jharris01, and Cloudschatze for providing valuable information and quality assurance.