What ckobu said only works with MIDI files. If you say you see v.cancel then you are loading an MP3 or WAV file and this sync button does not appear.
The only way I think this can be done is to use the Multipad Audio Link.
Go to Menu, Multipad Creator, then select Audio Link Multipad, once you have you song programed to one of the multipads.....
Press the sync start button on the multi pad loaded with the song you want to play then when you play a key the multipad will play. Then save to a registration.