OP is right.
If your lucky you might hear a little music every 30-45 mins but it's far too infrequent.
One thing that annoys me though is that when it does come on it's usually battle music which i never understood why devs put in there.
In a MMO you almost ALWAYS in combat so you start to hear a good track and then the annoying as all hell battle music comes on and then disappers.
Bioware, do us all a favor and disable the crappy battle track.
PS - I am also HIGHLY disappointed in the overall quality of the music. It just sounds like regurgitated movie music and has to theme or no soul.
This is one area that has been severly lacking so far, that other game by Blizz put TOR to shame when it comes to music and it's implementation.