Playing music at end of print ... (no replies)

I want to be able to play a song over the speaker fitted to my MK3 I3 at the end of a print job and repeat it until I come and stop it.

With the music on the SDCard I can play it via the serial connection with :-
M23 /MUSIC.GCO
M24
and I can repeat it by reentering the same commands :-)

However, when I add this to the end of job gcode (in SLIC3R's setup) the job completes OK and the controller shows MUSIC.GCO on the controller screen but it doesnt play!

Here is my end of job GCODE :-
M104 S0 ; turn off heater
G91 : Switch to relative position mode
G1 Z10 F250 ; lift nozzle by 10mm
G90 : Go back to absolute mode
G1 X0 Y170 F2000 ; move bed Y axis out so work is accessible
M84 ; disable motors
: Tell everyone we've finished
M23 /MUSIC.GCO
M24

... is there something else I need to do to get it to play ??

Regards - puzzled,
Dave