[sdiy] Has anyone built a voice pitch tracker?

[Dan]

First, hi to all.
I´m trying to build a pitch tracker for voice, with the purpose to double its frequency retaining the formants. It should track pitches between, say, 100 Hz and 400 Hz. So I try to filter out everything that´s above. I encounter following problems:
1. I need to eliminate the second harmonic - and when I sing very low the second harmonic is within the range of interest, so it can´t be filtered out with conventional filters.
2. I need the result to be centered around zero as much as possible, and if I do that by hi-pass filtering it ruins again my thing too.
So if someone has built such thing and dealt with those problems any help or hints would be very appreciated.
Greets to all,
Dan
  
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