I would like to do the same thing... here is what I think I know, and what I don't... (i'm doing research, but not getting much help)...

From what I understand you will most likely need to use the FFT algorithm to determine the frequency of the input... however I have not figured out how to get the input from the mic (if you know holler)...

I suppose you could record, and then figure out the frequency, but I can't figure out how to read straight from the input....

Here is a site that should help with the FFT, but any more than that... i'd research general info about playing/storing/reading waveforms.

FFT:
http://www.intersrv.com/~dcross/fft.html

Waveform:
http://www.jwcs.net/developers/dap/intro/part1.htm


if you or anyone else can help me put this all together that would be great... I am just having trouble sorting it all out...