Real difference between MT-32 OLD and NEW MIDIs

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Real difference between MT-32 OLD and NEW MIDIs

Postby cryptowhale » 2015-7-17 @ 12:35

Hello!

I'm in the process of choosing MT-32 compatible device for my retro rig. Currently, after reading all the lists of MT-32 compatible games, I think that CM-32L/CM-64 is better for my needs because I won't be playing MT-32-OLD games much. Except for Dune 2.

Some would say that I should get both MT-32 rev.0 and CM-32L/CM-64 to cover every MT-32 game, including Dune 2, but I want to keep my setup as minimal as possible. If I get two of MT-32s, I will need some kind of external mixer that should be manually operated to switch between MT-32s, while with one MT-32 it's possible to use sound cards' Line-in for mixing purpose (yeah, I'm going to use MPU-401 compatible sound card with SoftMPU, not the real MPU-401 device).

I saw several reviews regarding difference between MT-32 rev.0 and later models, but non e of them give any technical insight on what really causes games to sound differently on older models? So, what precisely are the bugs that those MIDI files use in rev.0 that are not available in later models?

For example here are two interesting reviews: this good known one by philscomputerlab shows difference in games that use custom sounds, and this one shows difference in standard sounds using Dune 2.

I tried to replicate second review's comprasion with Dune 2 using Munt. I got roms from old MT-32 anf CM-32L, tested the same Dune 2 track that was used in review on both of them and... it sounded identically. Even more - it sounded like on real CM-32L, even though old MT-32's rom was used. So the difference between old MT-32 and CM-32L lies deeper than just difference in roms.

So does anyone have any technical insight in what "bugs" in MT-32 rev.0 some games were using? I know, from Munt sources, about the difference in reverb and, from Wikipedia article, about the difference in CPU and DAC. But that doesn't explain (to me) why some sounds (distortion guitar) in Dune 2 sounded louder on MT-32 rev.0?
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Re: Real difference between MT-32 OLD and NEW MIDIs

Postby PhilsComputerLab » 2015-7-17 @ 12:44

Hi!

I can't give you any technical explanation, I'm more an observer / researcher / documenter. As for your choice, I would also go with a CM-32L. It's the more versatile unit. And if you then see a MT-32 for a good price, maybe add that to your collection.

I would get an external mixer regardless. I don't know how good of a quality the internal mixers of the sound cards are, but mixing externally is great as you can adjust things during game play. Many games change volume levels, so this is a handy feature. I also mix in the CD Audio output externally, quite nifty :blush:

Back to your question, when I played around with Munt, and compared MT-32 (Old) with CM-32L ROMs, I could hear differences. The Heart of China is a good example. When you first travel, there is a sound when your passport gets stamped. On a CM-32L it sometimes just clicks, whereas on the MT-32 (Old) there is a solid THUMP sound.

Once you're landed you can hear some cows and other noises. They also sound different.

I'm pretty sure I also tested the Space Quest 1 VGA bug.

Cloudschatze and NewRisingSun are members that can answer your question :)
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Re: Real difference between MT-32 OLD and NEW MIDIs

Postby cryptowhale » 2015-7-17 @ 13:35

Phil, thanks for the information!

I will try The Heart of China with Munt myself just to be sure that I didn't messed up some configs when was testing Dune 2.

The real reason behind my question is that I'm trying to research the possibility of "fixing" MIDI music for the games that sound correctly only on old MT-32, so that they can sound correctly on later MT-32 models.
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Re: Real difference between MT-32 OLD and NEW MIDIs

Postby jesolo » 2015-7-17 @ 19:36

Unfortunately, I also cannot offer any technical explanations but, if I had to guess it probably has something to do with the CPU or the DAC (since this was the only major difference between the earlier and later revisions).
I own both a CM-32L and an MT-32 ("old type" rev 1 PCB) but, I mainly use the CM-32L because of the extra sound effects that some games support. The MT-32 is probably "cooler" because of the front panel LCD display.

However, just on the topic of owning one of these modules.
If you don't already own one of these modules, then you will probably find that the CM-32L or CM-64 modules are becoming very scarce.
I haven't seen CM-32L or CM-64 modules on eBay for a couple of months but, there are still some MT-32 modules available.
You might be able to source a CM-32L or CM-64 from other places but, be prepared to pay a hefty premium for one.
If you don't already own one and can grab an MT-32 for a reasonable price, then I suggest you do so.
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Re: Real difference between MT-32 OLD and NEW MIDIs

Postby sergm » 2015-7-19 @ 08:49

Unfortunately, even I can't offer detailed explanation about every single feature of old MT-32 :)

Nevertheless, aside from already implemented in munt different reverb, output sound routing and analogue LPF, I'm pretty sure all of them are "bugs" (in terms of Roland?) of the control ROM. To be fair: munt isn't an emulator in fact, it doesn't execute program code in the control ROM you supply. This approach is used in MAME/MESS, and you should be aware that it demands significantly more of CPU load. This means, all the control ROM bugs (e.g. missing input value checks/clamps) are NOT visible to munt and must be explicitly implemented (like one quirk of pitch overflow described in http://www.vogons.org/viewtopic.php?p=242300#p242300). However, munt loads some things right from the ROM, including all the standard patches, so they will sound identically to the hardware (as they certainly don't abuse the quirks) :)

As you probably realize, there is NO way to reproduce patches which exploit those quirks on the latter units, (otherwise there would be no sense to abuse them). We're actually working on implementation of other quirks right now using the way of MAME/MESS. But it isn't so straightforward because of quite enough differences between old and new MT-32 arch (with new arch it works quite well by now, though my CPU is overloaded). Eventually, everything should be accurately emulated after some time.

BTW, note that LAPC-I/CM-32L can actually be equipped with the LCD and the button panel, so this isn't an exclusive feature of MT-32. It's control ROM is quite similar to new MT-32 (rev. 2.04) but the latter has the demo tunes. LAPC-I/CM-32L can even be instructed to play those demo tunes :)

Concluding the above, if you're not interested in Sierra's games, CM-32L unit would be better (not mentioning availability and the price). The only DistGuitar patch from Dune2 isn't worth cutting down all FX patches available in CM-32L. BTW, I tried to "fix" that patch in munt with no success, I think it can be improved by adjusting the TVA level though. So, patching Dune2 might make you absolutely happy :)
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Re: Real difference between MT-32 OLD and NEW MIDIs

Postby cryptowhale » 2015-7-20 @ 11:48

Wow, guys, thanks for all the answers!

Sergm, so CM-32L board has connectors for the front pannel? And what is TVA level?
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Re: Real difference between MT-32 OLD and NEW MIDIs

Postby sergm » 2015-7-20 @ 12:07

I just noted that control ROM contains all the support code for LCD and buttons (and even for missing demo songs). IIRC, someone has already discussed "upgrading" a CM unit with LCD somewhere on this forum...

TVA (time-variant amplifier) envelope in that DistGuitar patch looks weird to me, and I still haven't realized why old units play it louder. But no doubt, the overall output level can be made louder for that patch as the base TVA level isn't set on the maximum.
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Re: Real difference between MT-32 OLD and NEW MIDIs

Postby PhilsComputerLab » 2015-7-20 @ 12:27

Funny fact. When you play Privateer with a MT-32, there is a message displayed when you quit the game :happy:
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Re: Real difference between MT-32 OLD and NEW MIDIs

Postby Spikey » 2015-7-26 @ 00:52

When you play Privateer with a MT-32, there is a message displayed when you quit the game

As with several Sierra games, too!


Crypto: Bottom line, just get a second revision MT-32 or use MUNT, don't worry about 'bugs' and whatnot, in the real world you are unlikely to notice, or care, you will just love having the great sound. After A/B ing all 4 (old, new, MUNT as old and new) the differences are extremely small unless you pick a delibarate problem example, or which there are again, very few.

Enjoy the device and the sound no matter what you use, there's some great music. Just make sure if you get one or use MUNT, that you're playing a game designed for that sound and not a game after 1992, i.e. a General MIDI game, because MT-32 will not be the designed optimal playback device (i.e. it won't sound great, even GM soundfonts will probably sound better).
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Re: Real difference between MT-32 OLD and NEW MIDIs

Postby NewRisingSun » 2015-8-02 @ 12:19

But Privateer does not claim MT-32 support, and only sends General MIDI data. The LCD messages comes from the fact that Origin used the MT32MPU.ADV driver for the General MIDI selection, as the Miles Design AIL 2.x system does not come with an actual General MIDI driver. Because MT32MPU.ADV still sends the MT-32 reset sysex message, this breaks the setup of anyone who uses a CM-500 in Mode A and runs software to disable the MT-32 channels for General MIDI games.
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Re: Real difference between MT-32 OLD and NEW MIDIs

Postby corentin » 2016-2-03 @ 20:47

In Dune 2, the credit song is the only one with obvious difference between MT-32 and CM-32L ? Or some other tracks have issues too ?
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Re: Real difference between MT-32 OLD and NEW MIDIs

Postby corentin » 2017-11-23 @ 22:34

This is an old topic but, about the Dune 2 Soundtrack, any tips to actually edit the midi files in order to fix the guitar track on the CM32L ? What software can i use to edit mt32's .mid ? (I don't need to patch the game, just trying to play the midi file on a player at this point)
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