Hi,
I've been studying/reverse engineering some of my favorite SCC songs, and ran into something interesting.
The lead instrument in the first level of the game "Quarth" exhibits what looks like a triangle envelope modulating its volume. Initially I though it was being changed every "tick" (1/60 of a second), as it's normally the case, but inspecting the wave form in an audio app revealed that the volume was changing much more rapidly, about 5 times per tick.
How was this accomplished? Could MSX games manipulate the sound data at a rate higher than once every frame?
Check the images. The first one has a zoomed out view showcasing a few ticks, and you can clearly see the volume oscillating a few times per tick. The second image is a close up view, and you can see that the envelope only fully loops after 64 columns - instead of the usual 32 columns that the SCC provides.
The audio was isolated using and emulator (OpenMSX) outputting individual wave files for each channel.
Thanks!
