There is a Islands of Adventure CD available at the park, probably elsewhere as well, that has most of the area theme music on it. This thread will give me away for being such a fanatic of Uni, but YES I have it and I jam on it when I want to get into a vacation mood (reminds me of the parks) Unfortunately it does not have the red fish blue fish song, (at least the older version I have doesn't, mine is I think from 2003) but it has 4 from the Suess area that you will hear as you walk through that section. Circus McGurkess Cafe theme song, Suess Quartet, and 2 others I can't remember at the moment. It also has about 4 for each section at IOA.
Whats so cool about this is I saw a doc about making the IOA park. And when composing the area theme music, the guys said that they looked at every Dr. Suess book at where he drew instruments, they actually made these instruments and played them for the theme music, you can't really tell there are any original instruments on there but its still the coolest thing I have ever heard (one of them anyway)