Sierra games sound wrong

[vultureg7]

Hello!
So, I've connected my real Amiga 1200 to mt32pi with a null modem cable and a usb2serial (ch341 based) adapter. Everything sounds fine when I'm using midi players from the OS, or ScummVM, but sounds wrong with Sierra games. Here's an example from King's Quest V:

https://youtu.be/aCX6bqI-33k

As you can hear, it's not totally wrong, but some instruments are. On the mt32pi side, I tried all these to no improvement:

• changing from munt to fluidsynth
• outputting audio via hdmi instead of pwm
• mt32 alternate channels

I would blame it on my cable or the serial2usb adapter, but the very same equipment works flawlessly with Munt and hairless midi under my windows 7 pc.

Any ideas what I'm doing wrong and how to fix this?
Thanks!

[farvardin]

@vultureg7 just a wild guess: I've noticed most Sierria games were changing the default MT-32 sounds, using sysex commands (the MT-32 is a real synth, but it can't store the changes, you have to inject them through sysex). Maybe the midi adapter or the Amiga don't support this feature?