C/C++/Obj-C Real-time algorithm to ascertain Note (not Pitch) from Vocal Input

Question

I want to detect not the pitch, but the pitch class of a sung note.

So, whether it is C4 or C5 is not important: they must both be detected as C.<

Answer 1

If you are looking for the pitch class you should have a look at the chromagram (http://labrosa.ee.columbia.edu/matlab/chroma-ansyn/)

You can also simply dectect the f0 (using something like YIN algorithm) and return the appropriate semitone, most of fundamental frequency estimation algorithms suffer from octave error