The Little Harmonic Labyrinth means several things in this context. On the one hand, it is a semi niche piece of music composed Sebastian Bach.
But in the context of Gödel Escher Bach, it is a chapter dedicated to a dialogue between Achilles and The Tortoise about recursion and self-reference.
A personal favorite excerpt from this chapter was the dialogue involving the Genie and the idea of GOD. But in this case, GOD is actually God Over Djinn, a recursive acronym serving as the mechanism for holy requests.
Music
The musical piece itself is described in this chapter by how it leaves the reader/listener in a state of confusion, as it seems to be going in circles, but never quite returning to the starting point.
Just like how our logical brains are looking for a base case or a stopping point, the music seems to be trying to trick us into thinking it is just about to return to its starting point, but it never quite does.