native methods
midi_read(This,F) :- native(_,This,read(F),_).
midi_analyse(This,I,O) :- native(_,This,analyse(I,O),_).
midi_open(This,F) :- native(_,This,open(F),_).
midi_header(This,M) :- native(_,This,header(M,0,480),_).
midi_track(This,X) :- native(_,This,track(X),_).
midi_tempo(This,X) :- native(_,This,tempo(X),_).
midi_event(This,D,C,M,T,V) :- native(_,This,event(D,C,M,T,V),_).