[USB][MIDIio] PulseAudio was fixed by specifying two values in /etc/pulse/daemon.conf: default-sample-format = S24LE and default-sample-rate = 96000. The ALSA MIDI port "STUDIO-CAPTURE MIDI 2" allows to capture and send front panel settings changes as System Exclusive messages, while "STUDIO-CAPTURE MIDI 1" accesses the normal MIDI I/O.