# Autocorrelation & Pitch

*Module of the free GPU.js GPGPU course · 5 tasks*

Finding the note in a sound by asking how well it resembles itself, shifted — and the octave error that catches every naive detector once.

## Tasks

1. [Compare a Signal With Itself](https://gpu.rocks/learn/autocorrelation-b159433f/1.md)
2. [From Lag to Pitch](https://gpu.rocks/learn/autocorrelation-b159433f/2.md)
3. [Three Ways to Get It Wrong](https://gpu.rocks/learn/autocorrelation-b159433f/3.md)
4. [The Note That Isn't There](https://gpu.rocks/learn/autocorrelation-b159433f/4.md)
5. [Payoff: The Same Curve, via the FFT](https://gpu.rocks/learn/autocorrelation-b159433f/5.md)

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Interactive version: https://gpu.rocks/learn/autocorrelation-b159433f