The music from Jabu Jabu's belly from Ocarina of Time as Womb.
Quick beginner mod. The track is a little quiet compared to the rest of the game, so feel free to turn it up a bit.

Lastly, I only have Rebirth right now and I'm not sure if Afterbirth would affect if it works, but just to be safe, I've labeled it as Rebirth only. Feel free to try tho.