I have completed my VST Audio Effect plugin in preparation for final presentation Monday Dec 8th.
I added an enable/disable button for the pitch-shifting to save on CPU resources if that part is not needed.
I also added a ‘Bass Mix’ slider to mix un-processed bass frequencies back into the vocal-removed signal.
Depending on the song sometimes the vocal removal works well but also removes the beat.
To do this I created a low-pass filter that takes the original signal from the Host and adds it to the vocal-removed signal with a gain equal to the Bass Mix Slider (0-1.0).
For extra convenience the cutoff frequency of the LP filter is configurable using an additional slider that goes from 50Hz to 500Hz. At 500Hz some vocals start creeping back into the mix.
[Update 07/23/2013] Juce Pitcher source code is now available at https://github.com/pehrtree/juce_pitcher