MSX-Music Hi-hat question

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By Huey

Prophet (2694)

Аватар пользователя Huey

30-12-2022, 09:45

I was playing around with the FM tone registers for the percussions and noticed that both register pair $17+$27 and $18+$28 influence the sound of the hi-hat.
The YM2413 manual does not mention that. And other percussions are working as described in the documentation (single pair).
Anyone cn confirm this? I tested this on both emulation and real HW.

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By Parn

Paladin (853)

Аватар пользователя Parn

30-12-2022, 15:12

Yes, and they also both influence the sound of the cymbal. I don't know the exact reason, but I suspect it is related to the particular way these sounds are generated. I think there is some internal synthesis mechanism (used specifically by the cymbal and the hihat) which we normally can't access, but whose parameter is affected by both those pairs of registers.

By wolf_

Ambassador_ (10134)

Аватар пользователя wolf_

30-12-2022, 15:29

I think it's like this: channels 7, 8, 9 have 6 operators in total. And if you want 5 drum sounds, you need some funky algorithms to get all these sounds. A hihat/cymbal would require even more than two operators. So I figure some or all of these 5 carriers are being sent as modulator to other drum sounds as well. In other words, carriers are also modulators. You'd probably have to look into openMSX's FM-code to see how things are wired internally.

By Bengalack

Paladin (801)

Аватар пользователя Bengalack

30-12-2022, 15:33

Hi-hat again? I'm not sure if it is related to what you are describing, but a while ago I had strange sounds coming from drums on the YM2413. Grauw helped out and the troubleshooting can be read about here: https://www.msx.org/forum/msx-talk/graphics-and-music/ym2413...

By Huey

Prophet (2694)

Аватар пользователя Huey

30-12-2022, 16:35

Thanks guys for confirming.
Will look at that thred too. That is indeed another quirk I needed to tackle.

By Manuel

Ascended (19674)

Аватар пользователя Manuel

30-12-2022, 19:01

BD uses ch7 car+mod
HH uses ch8 mod
SD uses ch8 car
TOM uses ch9 mod
CYM uses ch9 car

By Huey

Prophet (2694)

Аватар пользователя Huey

30-12-2022, 22:24

@Manuel: That is what the HW manual says. But did you try it?

By Manuel

Ascended (19674)

Аватар пользователя Manuel

31-12-2022, 00:18

That's what the emulation does Smile I didn't know it was detailed that much in the hardware manual, so never mind that post.

By Huey

Prophet (2694)

Аватар пользователя Huey

02-01-2023, 15:03

Did you check the code?
Because in openMSX I hear direct change when I change both register pairs.

By ducasp

Paladin (712)

Аватар пользователя ducasp

02-01-2023, 15:58

Huey wrote:

Did you check the code?
Because in openMSX I hear direct change when I change both register pairs.

I think there were some changes due to a guy that made the delid of that chip and making an accurate reproduction of it, so it probably is no longer based on the manuals but on the real chip inspection, too bad no one wants to sponsor / do a s1990 and r800 delid, it would be quite nice

By Manuel

Ascended (19674)

Аватар пользователя Manuel

02-01-2023, 18:34

The default implementation is NukeYKT's, which is indeed based on a decapped chip, AFAIK.

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