Nicely done. One correction: the sound(s) that arise from two different notes sounding together are sum and difference tones, not overtones. Each individual t

Nicely done. One correction: the sound(s) that arise from two different notes sounding together are sum and difference tones, not overtones. Each individual tone has a collection of overtones (i.e. the harmonic series), and those and the fundamentals can interact to produce an audible beat when they aren't in tune, which can be the sum or difference of two frequencies that are almost but not quite in sync with each other.