[robotsteve2]

Spherical harmonics are a useful mathematical basis set for eigenfunctions of a Schrodinger equation describing a hydrogen atom like system.

There's nothing particularly special about them, and they fail to be a good basis set for solutions of other types of quantum systems. Conversely, they can be useful for non-quantum systems - any sort of wave equation in a sphere.

It's not an intrinsically quantum mechanical thing.

[dr_dshiv]

Idk… seems intrinsic in so far as waves are intrinsic to Quantum Mechanics.

Check out these visuals from “the orbitron”: https://winter.group.shef.ac.uk/orbitron/