How can I convert audio to a series of notes using pitch detection?
This should work using a threshold on the by-bin-difference of the magnitude spectrum.


Calculate the abs fft for current window and normalize it.
Do a bin-wise difference with the normalized abs fft of the last window.
Sum up the bin-wise difference and compare it to a threshold.


Explanation: A change of note means a change of energy distribution over the fft bins. So the sum of bin-wise difference should be high, if a change of note has occured. Normalisation is to suppress false detection of note change due to change of volume.