How does Mixed In Key determine the key of a track?
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Mixed in Key is a piece of software that analyzes mp3s and determines the key of the song, e.g. it will run and tell you if the song is, roughly, in F-minor or A-major.

The purpose is to aid in https://en.wikipedia.org/wiki/Harmonic_mixing

Is there a standard algorithm for inferring the key from a PCM waveform?  

Warning: music theory and signals processing noob here:

Is it as simple as taking the DFT and attempting to map the most common frequencies to notes, and treating the most dominant notes as the key?
