Sponge

• Watermelon 0:26

Plays while you are inside.

It fades in within about a second and plays over wandering music and over a place's fixed music. When you leave, the earlier music fades back in from where it had reached. A divine world has no structure music.

This is the Sponge structure. The Sponge biome is a different place and has no music of its own.