Wrong FM instrument in California Games

[Former user]

Original [issue 263](https://code.google.com/p/genplus-gx/issues/detail?id=263) created by superballena on 2012-07-27T23:06:29.000Z:

I've already pointed this one out over PM, but just so this issue doesn't get lost.

What steps will reproduce the problem? 1.Start a new game (any mode). 2.Select Surfing event.

What is the expected output? What do you see instead? The music in the Surfing event has at least one of the instruments playing at the wrong volume.

What version of the emulator are you using (official, SVN revision,...)? Happens in every version I've tried.

Please provide any additional information below (Emulator settings, Console setting,...) Default configuration.

I'm attaching a recording I made a while ago from a PAL Mega Drive, for reference.

[Former user]

Comment # 1 originally posted by ekeeke31 on 2012-07-28T12:43:10.000Z:

Did you recorded this from a model 1 (with discrete Ym2612 chip) or from a model 2 (with ASIC integrated FM chip) ? Because i think this is one of the instrument that sounds much louder on model 2 for unknown reason. I think it's similar instrument that is used in Shaq Fu, Flashback, Ariel, etc, all these games whose suffered for years from the infamous blip blip sound on anything else than Kega until Nemesis figured the detune overflow that was occuring. It was discussed some years ago on spritesmind and there is at least one game (Battletech track 5 i think) that uses similar instrument but still sound as "blip blip" on MD2. I think it's the same happening here and it's very likely caused by very high frequency sound being filtered differently on different models and being somehow amplified (you can actually hear the sound in emulators, just that it is very attenuated).

[Former user]

Comment # 2 originally posted by superballena on 2012-07-28T14:21:06.000Z:

It was recorded from a model 1 PAL system with no TMSS and with EXT port.

Came with Altered Beast, I believe it was the first European run of Mega Drives.

[Former user]

Comment # 3 originally posted by ekeeke31 on 2012-07-29T07:30:24.000Z:

Ok, it must be something else then, a bug somewhere in Ym2612 core. I tested the game on my MD2 ane it sounds the same. It also seems to sound find in other emus (did not test Regen though).

[Former user]

Comment # 4 originally posted by ekeeke31 on 2012-07-29T07:31:07.000Z:

[Former user]

Comment # 5 originally posted by ekeeke31 on 2012-07-29T10:08:15.000Z:

Actually, only Kega got this one right. It sound wrong in all other emulators (Gens, Regen, etc). It's like the pitch is not correctly emulated.

[Former user]

Comment # 6 originally posted by ekeeke31 on 2012-07-29T20:23:35.000Z:

[Former user]

Comment # 7 originally posted by ekeeke31 on 2012-08-01T19:11:58.000Z:

It appeared to be an issue with LFO emulation, from the original core. It seems only Kega got this sound right, other emus will make it sound a little louder but with an incorrect tone.

Fixing it also makes Spiderman & Venom: Separation Anxiety intro even sounds better now and I suspect it could affect some other games that disable LFO but still leave amplitude modulation active on a channel/operator basis.

[Former user]

Comment # 8 originally posted by ekeeke31 on 2012-08-01T19:12:18.000Z:

[Former user]

Comment # 9 originally posted by ekeeke31 on 2012-08-02T21:08:52.000Z:

fixed in r707