Wow, blast from the past indeed.

I seem to recall that Mark of the Unicorn made a MIDI dongle that plugged into the printer port, and the sequencer I used was Cakewalk.

I wasn't doing MIDI on my Mac Plus, so the question is a bit beyond my personal experience. However, I do know that Southworth Music Systems was already making hardware & software for the Mac back in that day. You can find reference to them here:

paul-lehrman.com/background.html

And don't miss the photo of Herbie Hancock being demo'd a Mac Plus for MIDI in 1985!

I still have a Southworth JamBox 4+, as is described here:

www.freqsound.com/jambox.html

I never used the MacPlus per se, but I used to have a Performa & an Opcode Studio 3, which connected to the printer & modem ports of the machine (the printer & modem would, in turn, plug into the corresponding port on the Interface). In those days, I was using Opcode OMS to manage the data between the applications & Vision as a sequencer (several iterations: plain old Vision, Vision DSP & Studio Vision Pro: www.opcodeusers.com/opcode/vision.html). For an editor/librarian, I used Galaxy. I would record all my MIDI parts to 4-track or 8-track, and then add vocals & other instrumentation from there. Vision was an awesome program, and much of its functionality has not been matched until VERY recently. It goes to show you how advanced that application was at the time. Damn shame what Gibson did to them.

Hey, I just found my old copy of MIDI Pascal ;)