Last time, we were able to create a plot that allowed us to manually inspect the sound music spectrum of a note being played. However, this is insufficient if we need to program an app that will detect the pitch for us. To perform pitch detection, we need to save a snapshot of the specific musical instrument's sound spectrum for a known note and then use this calibration value to detect any other notes that are being played. Here, we do just that by making use of the cross-correlation theorem which allows us to detect the unknown note pitch that was being played on my violin.
![](https://i.ytimg.com/vi/rOiMEyOBRBM/maxresdefault.jpg)