Interesting in theory, though it could get annoying fast (The first thing I do is always to turn off the bell). Changing tone based on depth could be pretty in

Interesting in theory, though it could get annoying fast (The first thing I do is always to turn off the bell). Changing tone based on depth could be pretty interesting, as could tones representing things like unused variables. Based on your preferences, you could also do things like have the noise grow unpleasant if you do something you shouldn't (e.g., reuse a variable name, write an impure function, etc.).