See the example "Sound Card AutoPower Spectrum" This allows you to sample from an input device through your sound card, and take a spectrum. you should be able to bin the spectrum by frequency bands, and show the histogram of frequencies. You probably can even selectively resample and scale the frequencies, mix the signal and output the new sounds but I hav not tried this (I am not an audiophile so this is beyond my scope of expertise) Good luck ,
