Our continuing series on the massive boondoggle that is retro PC hardware requires an extended talk on the MT-32. While I discussed it in the context of early MIDI capabilities on PC, one of the things the SoundBlaster cloned in order to get a death grip on the expansion audio market, the MT-32 is a very weird piece of hardware that requires an extensive analysis to really understand. It's a high-end synthesizer for its time that changing standards made obsolete, or at least broadly incompatible, very quickly, but for games out between its release in 1987 and the creation of the General MIDI standard in 1991, it's almost certainly the best option for sound. This post is the promised diatribe about why I hate it.
I want to be clear here: the MT-32 might well be the single most frustrating piece of PC sound hardware. It's still expensive, it's proprietary, and it's external to the PC. While it uses MIDI messages for communication, it predates the General MIDI standard specifying a consistent mapping for instruments. As a result, you cannot play back what we'd think of as a standard MIDI file on an MT-32 and expect it to sound good; the instruments will be all wrong. While anything that supports General MIDI is fairly easily replaced with another device that supports it, like swapping a Roland SoundCanvas for a Yamaha MU50, with generally comparable quality of output, that's not at all true for the MT-32. The MT-32 is not a reasonable device to play general MIDI files on, as it does not respect voice and channel mapping of the standard. This works both ways -- the average MIDI-supporting card or module cannot play back songs designed for the MT-32, either. They will not sound correct.
The closest thing to an upside here is that you can still use the same MIDI hardware to control the MT-32 as you can a more modern MIDI synthesis device, and we'll get into detail with that later. If you have some kind of a switch, it's possible to use the same interface to connect to multiple MIDI devices, powering them up as necessary for different games or audio software.
Being external is a problem because, well, you have to patch it back in. This isn't terrible -- most likely you'd just patch it from the RCA audio out to the line in connector on your sound card -- but it is a pain if you want to use your line in for something else. For that matter, the output is not digital, so there's the chance of added noise. And if you want to control multiple MIDI devices as in the previous paragraph you'd need some kind of external mixer anyway unless you enjoy regularly adjusting between patch cables. Even more hardware you'd need to get, but it'd probably be less noisy than trying to run it through, say, a SoundBlaster's line input. For being such a distinctive sound solution of its time, it's cumbersome, and outside of gaming quickly faded away, because that was the only context where the programmability for custom sounds was likely to matter at that price point; professional musicians wanting that functionality would rely on tools like the Fairlight CMI or Synclavier that were reaching ubiquity, and they had significantly better noise thresholds than the MT-32. The MT-32's niche was for computer gaming, becoming what to Sierra games the various finches were to Galapagos Island.
The funny thing, though, is like the multiple niches of Galapagos finches, the MT-32 managed to have multiple models released in this time frame, and games will have differing levels of compatibility with different modules. Newer models will never fail to play music for an older game, but between different models, digital noise was handled differently. There's a big description on Wikipedia that lays it out in pretty straightforward detail. The shorter summary is that for the original models, it was ideal to make sounds as loud as possible to compensate for analog noise, and the system had both a standard analog volume knob and also digital volume controls, to prevent the signal from becoming overdriven before reaching the analog conversion circuitry, which would produce noise. The later models did some minor changes to the digital filtering to better handle the noise, but lack the volume control for the digital signal, so it is possible for some signals to become overdriven that wouldn't on the original hardware. Ultimately, early MT-32s can wind up with noisier output from newer games, and older games can produce overdriven output on a newer model. I, alas, don't have any obvious example of a comparison of this between units, so please accept this recording of Space Quest III that appears to be played on a later MT-32, which sounds to me like it's suffering from overdriven distortion around 50 seconds in:
Another incompatibility that was associated with newer units was lower latency between the unit and the system it received commands from, so they could be written to with fewer delays; old units will lock up with an overrun error on some newer games, because those games send commands to the unit faster than it is capable of. We'll talk about getting around this at the end of the article.
Given that computer gaming quickly became the sole niche of the MT-32, some of these newer units were designed specifically for playing PC games on, and include a larger bank of sounds, useful for using the MT-32 to produce high-quality sound effects not available on older models. Due to their association with computers specifically, and often more precisely gaming, these models were named the "CM" line (for 'computer music'; 'MT' stands for "multi-timbral"), initially the CM-32L but also released as a unit that had one of their drum machines (the CM-32P) also built in called the CM-64. There is not a single MT-32 to rule them all, and at the prices they sell at it's hard to think of them as essential, and no game truly requires one to be played. If I had to pick one to get I would say the CM-32L because it will have slightly higher compatibility and some features designed specifically to work in games, but it's not necessarily the best-sounding option for games that came out post the General MIDI standard, where a more modern synth would be more appropriate (or might just use CD audio for its sound anyway). You can find a compatibility list on the VOGONS wiki, and it includes details on which models of the MT-32 are best suited to any given game -- though later games may be better suited to a General MIDI device (you can play King's Quest VI with an MT-32, but it was designed for a Sound Canvas device). However, there is no perfect MT-32, hence my big ol' rant here.
Here's a comparison on a game designed for the older MT-32 model, Space Quest III, between the older model and a CM-32L, with distortion audible around 2:10. The MT-32 also exhibits distortion in this recording, but the digital volume control would be able to compensate for that.
Either way, for a lot of games of the time, it sounds massively better than the Adlib you'd expect to be using for music otherwise, so it's hard not to covet one. The problem is, they're incredibly expensive for what they are, owing to their distinctiveness in the market. General MIDI was an open standard that anybody could implement; the MT-32 was proprietary in many senses of the term, especially because it did not play nice with other MIDI interfaces than the one Roland was using (because, again, many games used its programmable patch features to create unique sounds and would not sound right without it). MIDI, as fundamentally a set of instructions to play music and General MIDI adding a guideline to how those instructions are expected sound, has a massive range of devices that support it, because it is the professional standard for digital/computer music notation. With a modern midi interface, you can plug an old computer into your phone or tablet and use it to generate sound. There is so much flexibility in MIDI as a common interface, but the MT-32 does not use MIDI the way everything else does because of when it was made. The only solution is emulation.
Roland had some support for the MT-32 in some of their General MIDI modules. The SC-55 has a compatibility mode for the MT-32 that does not include any programmable instruments -- instead, what it does is map the MT-32's default instrument range onto SC-55 instruments so that things will sound mostly like someone composing for it would expect. The sound quality is inherently different, but if you didn't use the programmable voice features, it's fine. Here's an example of Monkey Island again on the SC-55 (also featuring a later Soundblaster emulating the MT-32, which we will get into):
The balance is a little off -- the percussion is a bit too loud, as is, IMO, the marimba, but, again, it's pretty good, and if you didn't play games that required programming custom voices it would probably suit you perfectly. SC-55 units aren't the cheapest expansion in the world, but they're a fifth of the price of most entries in the MT-32 line you'll find on eBay.
On the other hand, the more common emulation option is Munt, which is software attempting to replicate the sound of the MT-32 a bit more exactly. It's good enough that you probably wouldn't think much of it without a direct comparison, and does replicate the ability to do custom voices, and, being software, supports the various models as options. The downside is that, like a lot of emulation, Munt requires the presence of control ROMs from the original hardware, which are not technically freely available, but nobody has come after anyone for the distribution of the roms on the internet archive, so take that as you will.
Munt's biggest issue is that MIDI controls in modern versions of Windows are pretty frustrating to set up properly, and as a result it can be difficult to configure. Munt looks like it should support being able to set up multiple MIDI ports (i.e., allowing it to pretend to be multiple soft MIDI devices) so that it can present different MT-32 versions at the same time, but at least in Windows 10 (and probably some earlier versions), this is not an available feature, so the compatibility issues between models can require manually configuring it before playing a game which is, IMO, far less than ideal. I am not sure why Munt does not support multiple MIDI ports, and I certainly think it should, but it is unquestionably the easiest way to get MT-32 sound out of any device that can accept MIDI input.
Munt, however, is something that is not well-suited to an old processor like we might find in the DOS gaming PC that we want to work with. Munt is relatively CPU-intensive (I mean, there's a reason it had to be an external device in this era, and was never cloned through software the way Roland's Sound Canvas was in later versions of Windows). As a result, you'll need a device that you'll still have to patch the sound of back into your PC if you want to use a single output to speakers. So you'd want a device that has line out to plug into a sound card's line in. Phones and tablets don't normally have line in, and while they do have their own speakers that might be OK, placing the device somewhere to get decent audio balance would also be a challenge, and also the speakers on your phone or tablet are unlikely to be as good as whatever you're listening to all the other sound on. This MT-32 annoyance is back.
And, again, it's not perfect. It's very good, though, as this comparison between a real MT-32, Munt, and a soundfont based on the MT-32 (set up in both the MT-32 instrument mapping and a General MIDI soundfont that's not going to be appropriate for these games, and definitely not for anything using custom voices) shows. With Monkey Island, MUNT is a bit lacking in treble and seems to have less reverb. Again, though, I don't think the difference would be obvious without the head-to-head comparison.
There is one final MT-32 point before we go, about the programmable voice features. This required specific hardware provided by Roland to work, and cards like the SoundBlaster did not actually replicate it fully, making them incompatible with the MT-32. There is software that can get around this issue! Enter SoftMPU, a device that both allows these interfaces to replicate the so-called "intelligent" mode that lets them have full access to MT-32 features, and also allows for using a serial port to connect to a MIDI device rather than the standard sound card port. It can also prevent the speed issues with older MT-32 models preventing them from working (but won't fix compatibility issues with volume and reverb between models).
The full usage instructions for SoftMPU are available on Github. It's not quite essential DOS software, as it isn't very necessary to use outside the context of an MT-32 or in conjunction with a connection to something running Munt, and I'm not aware of any software that fails to work with it, though the usage instructions include some caveats.
The Orpheus card, mentioned at the end of the last post in the series, has an option for an extra chip that allows it to run its MIDI out in full compatibility with the MT-32 making SoftMPU unnecessary, though I am not certain if it can delay instructions to prevent the data overruns that the older MT-32s can have. The chip in question, the PC MIDI is available on a separate card as well. Given the price point and the compatibility factor of SoftMPU, it's probably not a necessary purchase except on lower-spec systems, but there is a use case for it that we'll look into on our next entry in the series.
But again, we ask ourselves -- if we're willing to emulate an MT-32, to emulate the MIDI interface necessary to drive it, why are we so concerned with period-correct hardware for other stuff? The argument might be, in fact, to go the other way around: get the real MT-32 (or CM-32L, or CM-64) and use a modern computer to drive it. After all, the MIDI standard it communicates with is the same as it was back then. Just as any device with Munt can be driven by period-correct hardware, a new computer can use a MIDI interface to communicate with a real MT-32. DOSBox sends MIDI out to the host machine running it, based on which MIDI interface is given to it, which can include sending it out to an external device like the MT-32. MPU handling will be done in DOSBox, and the commands will go in and out from the host, which does nothing but message forwarding. Here's a video demonstrating this in Windows 7:
To get the audio into whatever playback device you're using, you can then patch the audio into a line-in either on your computer or a USB interface for one if not available.
And finally, if you are the sort of person who is willing to sacrifice your firstborn child to an amoral gnome in order to wield the power of authentic MT-32 linear arithmetic synthesis, don't forget that the gnome's name spelled backwards is Nikstlitselpmur, and if the alphabet is also inverted, it's Ifnkovhgroghprm. Whether or not such a deal can save you the half a grand you'll expect to pay for an MT-32 is up for further analysis, but if you can, knowing this information may save your child's life.