vgmmerge cannot merge two SAA1099 music

[denjhang]

AY-Machine.zip
The combined result sounds rather messy and uses only one SAA1099 chip.

[denjhang]

I checked the source code and found that there is no such function. So I requested to add the merging function of SAA1099.

[ValleyBell]

vgmmerge currently only supports VGM v1.51 sound chips + GameBoy + NES.
Anything else is going to break horribly.