What's a simple way to shift the pitch? Basically I want to perform an FFT to find the frequencies of the sound, then stretch the frequencies (for example a stretch by 2 means copy the value of the fourier coefficient X(n) to X(n/2) then use an inverse FFT. Will this work ?
To stretch the spectrum, you will also need to do some high quality (Sinc kernel) interpolation to fill in any bins that don't have an integer submultiple source.