You can't convert midi tracks from external hardware. You have to record the output of the instrument onto an audio track. 1. on a blank audio track, select the input that corresponds to your midi synth. 2. Press the record button on the track 3. set the input levels o your audio interface 4. when everything is good, hit record on the arrange page and let it record the midi sequence. Now you have an audio track of your midi sequence. As far as know, you have to do 1 track at a time, but I can be wrong. CP.