Usually when i play the Caves of Skops areas, there is a glitched out buzzing noise whenever the music tries to loop. The track ends and a very shrill buzzing noise plays and the second track isnt played, just goes back the first track. This is notable in the first level of Crystal Palace and Mr Skops Stalactites (and i think the 4th level of eat at joe's), but doesnt occur in any of the other worlds.
This glitch always happened using from ePSXe 1.7 to 1.9. I use an original Rayman disk and the core sound and cd plugins for ePSXe 1.9 to run it.
I do not own a PS2/PS3 to run the disk on and my PSX does not have composite to be able to used on modern TVs
Demonstration:
https://www.youtube.com/watch?v=yC48EuhwOKY - Skip to 1:19 (btw its not my own video, it belongs to Haruka Tavares)