First: Sea World's show music is almost always produced exclusively for Sea World, and is rarely available in any form to the public.
Second: Background music is a slightly different story. I managed to get hold of one of the audio techs for the Orlando park once, because I was curious about some outstanding New Age instrumental stuff I'd heard through the walkway speakers. Turns out it was 99% off-the-shelf music from such artists as Pat Metheny, Michael Manring, George Winston, etc. I was able to track down everything I wanted from Ebay.
In short: Ask around! Don't take "I don't know" for an answer! Do as I did -- call Sea World, ask for the Audiovisual department. I'd be stunned if you couldn't find out what you wanted to know.
Walt Disney World
Tokyo Disney Resort
Theme Park Insider Books