Eigendrum

Eigendrum lets you draw any outline and hear it as a drum: the browser solves the shape's actual vibration modes with finite elements, so every frequency comes from your geometry rather than a sample. Shapes can also be defined by polar or parametric equations, every drum is scaled to the same area so only the shape is audible, and where you strike changes which modes ring. It even includes the pair of differently shaped drums that sound identical, from the 'can one hear the shape of a drum?' problem.