kstatus -- the type of MIDI message. Can be:
128 (note off)
144 (note on)
160 (polyphonic aftertouch)
176 (control change)
192 (program change)
208 (channel aftertouch)
224 (pitch bend
0 if no MIDI message are pending in the MIDI IN buffer
kchan -- MIDI channel (1-16)
kdata1, kdata2 -- message-dependent data values
midiin has no input arguments, because it reads at the MIDI in port implicitly. It works at k-rate. Normally (i.e., when no messages are pending) kstatus is zero, only when MIDI data are present in the MIDI IN buffer, is kstatus set to the type of the relevant messages.