[galangalalgol]

Also, thank you for taking the time to educate me. I didn't take any signal processing classes in my EE degree, so I learned everything on the job and have gaps. How does autotune not sound horrible, if they do it right it is indistinguishable, or so I have read.

[marcan_42]

Autotune works by resampling and doing time stretching (not sure if in the time or frequency domain, depends on the technology; there are many variant ways of doing this) in order to decouple pitch and duration to make adjustments, so it doesn't break harmonic relationships.

Audio time stretching (or equivalently, changing the pitch without changing time) is not a clearly defined process with a mathematical description (unlike plain resampling or modulation) but rather a semi-heuristic process that takes into account psychoacoustics. But yes, in practice, for small adjustments of a monophonic sample like a voice, modern algorithms sound really good.