MIDI and direct to serialport programming

[teroyk]

You should never ever use direct use of serial port when you code for Mac OS 9, because it works only if only one serial MIDI program is opened and most G3 and G4 macs are without
internal serial port. If you want use serialports in your program you should use Apple Midi Manager calls or Opcode OMS calls or Motu Freemidi calls, because all of them can reroute ports to another ports if needed. Of course you can program switcher what use or even you can use them together in your programs.

But if you still need information about MIDI and serialport programming here is some good links:

Very old obsolete, but is very informative why oldest Mac MIDI programs works only with real serial port. Oldest and lowest level information about 68k Mac and MIDI:
The Midi Connection:
http://www.mactech.com/articles/mactech/Vol.01/01.11/Midi/index.html
The Midi Connection, Part II:
http://www.mactech.com/articles/mactech/Vol.01/01.12/Midi2/index.html

A Midi Library for Pascal, still useful information if you had used this library and want make rewrite your program for Mac OS 9, this is still support only serialports, but all functions are listed so you can rewrite it to support AMM, OMS and Freemidi:
http://www.mactech.com/articles/mactech/Vol.03/03.12/MacIIMidiDemo/index.html