Hello,

in Biab, the imported Midi files are set on the melody or soloist line.
(you can check this by muting all instruments, one after the other until you reach (in the case of your file) the piano (melody) part). Then you do not hear anything more.

If you now (of course after you cancel the mute button) click on the icon "sequencer" (green circle) you get all available midi instruments of the song. In your case, the sax.

If you now click on the drop menu, you can easily change the instrument, like I did with your file and set it to a clarinet or anything else you like! Get it?
Have fun!
Bernard