Emulator

Just to be safe, here's my graphics config:
http://pastebin.com/crFQbhrK

This happens with both the XAudio2 and OpenAL audio backends.
And note that when it chooses the "wrong" key, it seems to always be the one on the far left.

It works perfectly if the audio backend it set to "no audio output"

That's really strange. I don't know what to say about that.

It's quite easy to reproduce, at least. Happens with the piano in chapter 6, and can be fixed by turning off the audio backend there too.

Weeks ago I've played the first piano puzzle (but I think it was befor chapter 4) using 4.0-4837 without problems (audio on).
You may try that revision to see if something has changed since then...

I'll try that, but what do you mean before chapter 4? There is no piano puzzle before chapter 4.

If the first piano puzzle is in chapter 4 then it is the one that worked perfectly for me with audio enabled using 4.0-4837...I don't remember very well...if the puzzle is in the same chapter where you turn on power for the elevator, it's in chapter 4, otherwise it is before...

When I get to the final piano segment later today I'll try it with some different revisions and see if I can find where it broke.

Not sure what changed, but as of 4.0-5163 NONE of the backends work, not even the "no audio backend" option.

Did you try 4.0-4837?

Yeah, confirmed, it works fine in 4.0-4837 (I tested with Xaudio2 backend). So it broke somewhere between that and 5099.

What the heck. Now it's working on 4.0-5163 again.
It must be something in the settings, then...

Cause found.
For whatever reason, if anti-aliasing is on, the piano will not function properly.

Ran through the piano game with anti-aliasing on and logging enabled. Anti-aliasing is definitely the cause.
log: http://pastebin.com/vrQUnD0P

Anti-aliasing being the cause makes sense. Anti-aliasing can causes issues if a game reads from the EFB or an EFB copy because it changes the rendering.

We might just need to fix the game's INI to force AA off.

So judging from the other issue for this game it needs mmu and to disable anti aliasing?

That's what it seems like to me, unless the MMU is just hiding the crash and not actually fixing it. I'm planning on trying to replicate the crash with MMU off in Interpreter mode one of these days.

Now if only I could find a fix for the stutter when fighting Bloomed ghosts. :P

I will make a commit about it, hope you are correct with your findings.