I have used search and I know the SID has polyphony, how do I send the midi messages and notes to go to one single oscillator?
So I can have drums, bass, lead, all playing from the box at once?
Hi:
The SID have 3 oscillators, so a maximum polyphony of 3 notes can
be played. But normally you want the 3 osc played mono to get
a more complex sound, thats why you can construct a multi SID
box, to obtain a polyphonic box (up to 4 SID=4voices) with 3 osc each.
But with MIDIbox SID V2 you can’t play drums, and a bass and a lead
at the same time (as you ask). You have to choose to run a drum
machine or a synth in the box. With a multi SID box you can play
diferent synth sounds on every one of them (but I’m not shure how,
because I build a single SID one).
In MIDIbox SID V3 will be possible to run a drum machine in one SID
a 303-like bassline in another and a lead synth in another all at the
same time, but in different SIDs, so you still need to build a multi SID
box.
Sebo is right, but the versions he speaks of are out by one 
In a multi-SID box (V1) you can have each SID on its own MIDI channel.
For a single SID, I think TK said once that you can assign each of the three oscillators its own MIDI channel, but this was only configurable from SysEx, not from control surface, and I can’t find out how to do this from the documentation.
In V2, it is planned that you can do this a lot easier, and one SID can have three single-oscillator “mini” patches for a C64-like sound.
These versions are software, not hardware?
So it’d just mean a code upload mostly?
The difference between V1 and V2 (sorry for the mistake before) is
mostly software, the only hardware difference is the PIC (V1 uses
18F452 and V2 uses 18F4620).
But you can make a V1 and when V2 comes out, you have to replace
the PIC ans upload the new soft.
Sebo
V1 uses 18F452 and V2 uses 18F4620
Just to complicate matters, you can run v1 on a PIC18F4620…