hehe. I don't think that will be possible... but you can never be sure...
Decoding tinytrack-data and puting onscreen would not be difficult at all (a tinytrack is on my wishlist for christmas).
But for just receiving aprs, it should really be enough to connect the speaker-out from an FM receiver on 144.800MHz to the mic-in on the empeg and it should be possible to decode that even with music playing...
But my time is mostly occupied with the baby these days :-)

Marius LB4PE/OZ4PE