Eliminating ghost notes in Cello Fortress
In my previous blogpost (which is already quite a while ago, sorry for that: I have been really busy on the graphics for Cello Fortress), I explained how my algorithm works for detecting what the cello plays in Cello Fortress . The big missing part there, was that the algorithm I use not only finds the notes that are being played, but also tons of notes that are not being played. Most of those erroneous notes can easily be detected and removed, so let's have a look at how to find and eliminate them. Octaves The first problem is octaves. Because of the way my algorithm works, for every note that is found, its octaves are usually also found. Octaves are notes at exactly double the frequency, and double of that, etc. For example, A2 is 110hz, so the octaves that are also found are A3 (220hz), A4 (440hz), A5 (880hz), etc. Finding octaves is inherent to how my algorithm works: I detect notes for which both the own frequency and the overtones (multiples) are strong. The octaves are all...