...

1.) Let each thread open a handle using snd_seq_open() 2.) Call snd_pcm_wait() in each thread

Are these functions

a) real time safe?

snd_seq_open() is not, but why would that matter? Don't you call it from the GUI thread?

Ah, indeed, seq_open() is part of the initialization, so for this one, it does not matter.

...

b) race-condition free, assuming I'll use pairwise different handles each thread

Yes.

You're really 100 percent sure that this is guaranteed to work? Sorry for asking this :) I was expecting a "No, of course not.".

Also, this will probably work for all handle-based-functions, as long as you keep using pairwise different handles?

Regards, Johannes