[alsa-devel] ALSA MIDI exclusive mode ?

I ready somewhere that some applications, like Bitwig, allocate(?) MIDI ports in "exclusive" mode so that other application cannot connect to the MIDI ports. I used Bitwig and confirmed that after starting Bitwig in qjackctrl you cannot connect any of the MIDI write/read ports. ( qjackctrl MIDI option is set to "none") I could not find any documentation on such "exclusive" feature though ?