Nah, sometimes it sounds like the space seagulls are more noisy, but that's only because the music has loud and soft parts.
They do seem to be sound effects rather than music though, as they don't seem to sound consistently timed with the music.
On a side note, why does world 5 has underwater music if you cant go underwater anywhere anyway? (Or can you?) just managed to get my boat form stuck somewhat under the ship, it has unique underwater music now.
Edit: lol, you can force the boat form underwater by racing into a ramp near the inept piratey ship.
Stop picking your nose