What is the shape of a drum?
A square drum sounds different than one with the shape of an hexagon, even if they have the same area.
A big circular drum sounds differently than a small circular drum.
A Black Hole (which is also a kind of drum), sounds differently depending on its mass and also on its spin.
This is a simple Mathematica notebook where you can test some of this things. Please check Wikipedia's page to read more about this very interesting question.
Needs this QNM package in Mathematica (although it is probably easy to adapt to any other package that computes QNMs of rotating BHs).
Tested in Mathematica 13.1
Please file an Issue or a PR if you find a bug or there is something that can be improved.