[sdiy] Using MIDI internally in a polysynth

[Colin f]

> What I want to know is: What do people think of using MIDI 
> internally  
> this way? Has anyone tried anything similar, or does anyone know of  
> any synths that do something similar? Would this scheme be too laggy?

Roland used MIDI busses internally between the assigner CPU and the voice
boards in the JX10.
The assigner CPU only had a single hardware UART, as did the 8051s on the
voice boards, so they used the rather inefficient setup of having the
external MIDI in connected to the assigner CPU, the assigner's MIDI out
connected to both voice boards ins, and the external MIDI out fed by one of
the voice board serial outs.
MIDI transmitted from the assigner CPU has to be forwarded to the outside
world by a voice board.
They used 'unused' MIDI status bytes to select the destination  - F1 selects
Lower Voice Board, F4 = Both Voice Boards, F5 = Midi out and F9 = Upper
Voice Board.
The communication from assigner to voice board doesn't use MIDI protocol.
It has a set of command bytes for each voice board parameter which are
followed by a single data byte.
Command bytes have bit 7 set, like MIDI status bytes.

If you want to know whether using this sort of scheme makes an instrument
too 'laggy', have a shot of a JX10.
Yuck.

Cheers,
Colin f