MSX-Music Hi-hat question

Prophet (2694)

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.

By Parn

Paladin (837)

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_ (10109)

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 (747)

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)

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 (19462)

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)

30-12-2022, 22:24

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

By Manuel

Ascended (19462)

31-12-2022, 00:18

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

By Huey

Prophet (2694)

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 (680)

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 (19462)

02-01-2023, 18:34

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