Wrote a very brief Applesoft program which just loops and prints out info read from DATA statements. Only a few lines long but seems to be almost sufficient to play a converted MIDI file, if fed the right data:

10 L = 1
15 READ D
16 READ V
25 IF L = D THEN PRINT V: READ D :READ V
30 L = L + 1
40 GOTO 25
50 DATA 20000, 1111, 50000, 2222, 70000, 3333