Polyphony algorythm and custom made SIDSynth

[ucSound]

Hi,

I've been working for some time now on my own version of the MIDIBoxSID. After trying to make one with any success, I figured out I could make my own from scratch. Everything is working fine on the PCB, I simply need to figure out some software issues before I can call this one complete.

Does anybody has experience in writing a polyphony algorythm? Basically I want the MCU to remember up to 16 notes and load the 4 / 12 most recent notes to the 4 / 12 available voices (4 with 3 osc per voice, 12 with 1 osc per voice)

Here's a couple of pics of the beast, there's actually 2 of them, 1 with 4 6581, and the other with 2 8580 (still looking for 2 more). SIDs are stuffed with parallel data and address, all by a ATmega164P. The flat cable is for the LCD.