He stole the car, I doubt the music was his. He probably just picked a song he liked.It does seem odd that a twelve year old punk would listen to classical music while stealing a car.
And the Cardassian poet living on Vulcan is a continuity anomaly which should be ignored. Aside from that, there is no evidence the Cardassians were known to the Federation before the 24th century.
Not counting the evidence you want to ignore.
