VOGONS


First post, by lordskylark

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The MT-32 has reversed stereo / panpots.
Does CM-32L or LAPC-I have this issue too?
Are there any other devices/soundcards at the time that would also have reversed stereo?
If not, was the MT-32's a manufacturing mistake?

Reply 2 of 10, by Falcosoft

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lordskylark wrote on 2020-04-27, 04:24:

The MT-32 has reversed stereo / panpots.

Compared to what? Yes, MT-32 has reversed Panpots compared to GM/GS/XG but not to its own specification. In MT-32 Midi implementation chart it is explicitly stated that Pan (CC#10) controller should be interpreted as 0 - Right, 63 - Center, 127 - Left.
In GM specification you can find the exact opposite. Since MT-32 predates GM/GS/XG you had better say GM/GS/XG have reversed stereo / panpots (compared to MT-32).

Actually I also do not think this is a serious problem since Midi files/games composed on MT-32 sound right on MT-32 since they follow the same rules for panning as the MT-32.

lordskylark wrote on 2020-04-27, 04:24:

Does CM-32L or LAPC-I have this issue too?

Yes, since they follow the same specification.

lordskylark wrote on 2020-04-27, 04:24:

If not, was the MT-32's a manufacturing mistake?

No. As I have said above it's simply a matter of different interpretation of a Midi controller message (compared to GM) , not a defect.

gdjacobs wrote on 2020-04-27, 04:32:

All kinds of SB Pro clones had reverse stereo.

I do not think it's the same issue. Those clone cards definitely have a "bad" implementation of SB Pro stereo standard. You cannot say the same about the MT-32's pan implementation. It's implemented exactly as its own specification demands.

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Reply 3 of 10, by gdjacobs

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Falcosoft wrote on 2020-04-27, 05:06:

I do not think it's the same issue. Those clone cards definitely have a "bad" implementation of SB Pro stereo standard. You cannot say the same about the MT-32's pan implementation. It's implemented exactly as its own specification demands.

Yeah, not identical by any means. My understanding is the SB Pro "standard" is pretty ambiguous.

It'd be interesting to find out why pan orientation was reversed between LA synth and GM devices. Was it a design mistake or was there a reason for the switch?

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Reply 4 of 10, by Cloudschatze

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The original MIDI specification didn't explicitly define use-cases for any of the continous controllers, leaving it up to individual manufacturers, who largely managed to standardize amongst themselves anyhow. The MMA did later adopt the recommendation of using specific controllers for specific purposes, including panpot and its orientation, but this was after the MT-32 was designed.

Reply 5 of 10, by derSammler

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Falcosoft wrote on 2020-04-27, 05:06:

Compared to what? Yes, MT-32 has reversed Panpots compared to GM/GS/XG but not to its own specification. In MT-32 Midi implementation chart it is explicitly stated that Pan (CC#10) controller should be interpreted as 0 - Right, 63 - Center, 127 - Left.
In GM specification you can find the exact opposite. Since MT-32 predates GM/GS/XG you had better say GM/GS/XG have reversed stereo / panpots (compared to MT-32).

MIDI commands are not there for interpretation, they form a standard.

MIDI CC 10
Pan
Controls the left and right balance, generally for mono patches. 0 = hard left, 64 = center, 127 = hard right

This is MIDI, not MT-32 or GM/GS. The MT-32 does violate the MIDI standard it is based on by reversing the values. GM/GS implements it correctly. Again, there's no interpretation here, any MIDI-compilant device must follow these standards. So yes, MT-32 has reversed panning (not reversed stereo!).

Reply 6 of 10, by BloodyCactus

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I mean the accepted answer is, MT32 predates General MIDI spec. MT32 / CM32 have their own standard. MT32 was made in 1987. GM was codified in 1991.

Dont confuse the MT32 being a midi compliant device (hardware spec) 1981, with GM software spec 1991.

It does not have reversed panning. It does not have GM compliance, and cant be compared to a GM compliant device.

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Reply 7 of 10, by Falcosoft

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derSammler wrote on 2020-04-27, 15:30:
MIDI commands are not there for interpretation, they form a standard. […]
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Falcosoft wrote on 2020-04-27, 05:06:

Compared to what? Yes, MT-32 has reversed Panpots compared to GM/GS/XG but not to its own specification. In MT-32 Midi implementation chart it is explicitly stated that Pan (CC#10) controller should be interpreted as 0 - Right, 63 - Center, 127 - Left.
In GM specification you can find the exact opposite. Since MT-32 predates GM/GS/XG you had better say GM/GS/XG have reversed stereo / panpots (compared to MT-32).

MIDI commands are not there for interpretation, they form a standard.

MIDI CC 10
Pan
Controls the left and right balance, generally for mono patches. 0 = hard left, 64 = center, 127 = hard right

This is MIDI, not MT-32 or GM/GS. The MT-32 does violate the MIDI standard it is based on by reversing the values. GM/GS implements it correctly. Again, there's no interpretation here, any MIDI-compilant device must follow these standards. So yes, MT-32 has reversed panning (not reversed stereo!).

You are wrong . You simply project the definition of Pan controller (from a later Midi specification) to an age when it did not exist. The Midi specification 1.0 has many revisions:

Though the MIDI Specification is still called "MIDI 1.0" there have been many enhancements and updates made by MMA since the original specification was written in 1982.

Here you can find the original one from August of 1983:
https://www.midi.org/articles-old/historical- … ments-uncovered
AS you can see nothing is mentioned about how CC#10/Pan should be implemented. (Read back what Cloudschatze has written.)
Actually controllers 4-31 are simply defined as Continuous Controllers MSB and "the controllers are not specifically defined. ".
Screen-Shot-2018-04-29-at-2.41.43-PM.png

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Reply 8 of 10, by gdjacobs

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Cloudschatze wrote on 2020-04-27, 15:26:

The original MIDI specification didn't explicitly define use-cases for any of the continous controllers, leaving it up to individual manufacturers, who largely managed to standardize amongst themselves anyhow. The MMA did later adopt the recommendation of using specific controllers for specific purposes, including panpot and its orientation, but this was after the MT-32 was designed.

So this was a convention from other JMSC and MMA members? Was Roland pretty much the only manufacturer who did their panning this way or were there others in the pre-GM era?

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Reply 9 of 10, by Cloudschatze

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gdjacobs wrote on 2020-04-27, 22:43:

So this was a convention from other JMSC and MMA members? Was Roland pretty much the only manufacturer who did their panning this way or were there others in the pre-GM era?

I'm not sure about other manufacturers, but I believe the MT-32 was Roland's first product to leverage CC#10 for panpot. I also suspect that the R/L orientation may have been a carryover of their use of CC#8 for stereo "balance" in the slightly earlier S-220.

It may have been sometime around late 1986 / early 1987 that the MMA adopted the "standard" CC#10 orientation, which Roland's relevant non-MT/CM-variant products from 1988 onward implement. I'm sure they had their reasons, but it is odd that they didn't just change the MT-32 to match with a suitable EPROM update early on.

Reply 10 of 10, by lordskylark

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Thank you, everyone, for all of the responses. After the discussion, I can at least rephrase my terminology from "reversed" to "opposite" in the panning. Then hopefully neither the Roland MT-32 familiy and the later GM families won't be upset.

So I think Falcosoft gave me the primary answer I was looking for -- that is, whether the MT-32, CM32-L, and LAPC-I all shared the same panning assignments -- which he said that they do.

However, was there ever an instance of mislabeling the R/L output stereo jacks? Someone thought that the LAPC-1 might have had mislabelled jacks.