My guess is that it's the sequencer. I also use DOSBox to run an old MIDI sequencer, and the timing is very good. But this same sequencer, when I ran ti under WINE in Linux, has terrible timing; I could never resolve the problem. So MIDI timing, at least for old MIDI sequencers operated in nonstandard ways/OSes, seems to depend very strongly on the details of how the sequencer operates.

No, the actual internal timing is wonderful! Rock solid.

It's only the midi *clock* signal that it's sending (to allow me to clock another sequencer to it), that is all over the place.

I'm guessing that DOSbox MIDI wasnt designed to send MIDI clock.

Which is a real shame for me, cos I love it otherwise!

by the way, I'm curious what sequencer you are using..

Well, it's actually an old, very simple notation program called ConcertWare (run in Win 3.1 in DOSBox). I use it just to quickly and easily get my musical ideas down into MIDI; I then switch over to my DAW software (Pro Tools) for further work and to integrate audio and MIDI (all done on my Mac, including DOSBox). So actually I never have to sync ConcertWare with anything.

But it's really cool (to me) that DOSBox has become part of my otherwise very expensive studio setup. (And yes, I do have some games on DOSBox).