Hi,

I've installed guix-system and did some further testing: 

The package seems to work just fine when properly installing jack2, pipewire (pw-jack) or jack on guix-system (and Fedora). It's possible to put jack (v1) in the propagated inputs, but that's not that elegant I suppose. Furthermore all the audio packages I could find in guix include jack in the same way, at build time and not as a propagated input.

I cannot test this with actual midi hardware, only with the midiout.open_virtual_port method. But for my use case (using the OLA suite), the library works fine, even when using real DMX controller hardware.

So after testing and configuring my system properly, I have found no reason for a revised patch. If you or someone else wants to take a look at this patch, please do.

Thanks.