I've recently been trying to get AY/YM music playing on the SID chip. (for my own amusement) Using data from the old YM format by Leonard/Oxygene, I'm streaming compressed register output in real-time to give a fairly ok sounding simulation of the AY.
Here are some examples of Atari ST music. My pre-processor does frequency and volume conversion, and using the Exomizer compressor most tracks export out to a 4-40kb size depending on complexity. (rather than song length)
Mad Max - "There aren't any sheep in Mongolia"
Tao - "Toxygen"
Scavenger - "DBA Intro 6"
There were, obviously, some caveats to getting them working on the sid:
The SID chip doesn't like jumping around the volume range per frame, I've got somewhat around this by doing a bit of ADSR banging and resetting the gate for a few cycles. AY envelope support is quite minimal at the moment, so some tracks don't quite fade how they would on the hardware.
There is basic 'buzzer' support (using the saw wave) but while it does frequency it doesn't take the envelope shape into account or mix the existing tone signal. So, currently, tracks like the "TCB Bobs Record" screen have quite a flat bass sound.
The AY chip has the ability to mix both tone & noise simultaneouosly on the same channel, to get around this I alternate noise/tone per frame when that's enabled.
SID-wave support is currently on/off based on if the timers are active, rather than calculating frequency and determining the channel from there.
I had some digi drum stuff working but it uses the 6581 volume channel trick, so currently only works on those chips.
Last edited by 4mat (Mar 12, 2016 2:46 pm)
