Spectral rotation

People use all kinds of controls for speech-like sounds. One of them is spectrally rotated speech, and I've always wondered wtf that is. So I figured, it must mean that the spectrogram is rotated, but how do you do THAT? So, methinks: consider the FFT; let the real part = power, and the imaginary part = phase. Clearly, we don't want to change phase info, but just swap around the power info. So that's what this little MATLAB script does :) And here's proof of the pudding: first, the normal spectrogram: And then the rotated version: frequencies between 0 and 4 kHz have been rotated (nb: the sound file was 16kHz, so the frequencies run from 0-8kHz; and so 4khz is approx halfway up) :)