I take it that this is a portable "boom box" - I don't think any of those things had decent cassette players to begin with, and now it must be at least 10 years old, and more likely 20. Wikipedia says that most of the major U.S. music companies discontinued production of cassette tapes by late 2001, and there were only 34,000 pre-recorded cassettes sold in the U.S. in 2009.

I'd suggest that you get a used cassette deck that looks like it's in pretty good condition (TEAC is a good brand), and clean it really well. Use a Q-tip and rubbing alcohol on the head, and on the capstan and the rubber wheel. It's really important that the rubber wheel be clean and soft. Play your cassettes on the deck (fast-forward and rewind them first), and record them onto digital media (onto your computer is good). Don't expect to be able to play them more than ones, so record them right away.

But that cassette that's stuck in your boom box is ruined, and the boom box cassette player isn't worth fixing because it was junk in the first place. Don't bother with it. You can probably find the music on YouTube.

Good luck.

-Joe-