It's been done
Yes, it's a novel piece of programming, but a user named Cyberdevil did this idea literally to death a few years back. Granted, yours is more all encompassing than his, but it's still a direct port to the Audio Portal, though severely limited.
A play / pause button should be able to play and pause the track. This just plays a new track from the start over the top of it, making the whole thing a horrid mess. You really need to work on the programming, to make things like this work, even something as basic as a program like this one.
Ideas to go forward that I could give you would include a playlist function - something that prior to the 2011/2012 redesign, the Audio Portal does not have, where you line up half a dozen or so tracks and let them fly. This could also be incorporated with a random "shuffle" function, where people could tab certain genres that they wish to listen to, which could generate a few bits and pieces to assist the user. A display feature, which shows a few key pieces of information about the track - genre, title, author, date and so forth would be useful, otherwise, I'm not seeing any benefit in listening to a piece from the Audio Portal, without actually going there myself.
What's the target market? Are you aiming to export this to other sites and have people come to Newgrounds from there? If so and your programming works, a great little piece of viral marketing. If not, this seems to be a dead end piece that you've merely used for practice.
[Review Request Club]