Decomposing a DFT into multiple FFT calls I'm using a good fast FFT implementation (vDSP) that will only work on power of 2 blocks of audio data.  Now I have a problem where I would like to be able to apply the calculations to non powers of 2 audio.

Some degree of reading around suggests that I can do this by breaking the DFT into smaller power of 2 blocks.  

Can anyone explain how to do this, if indeed it is possible at all? I have been unable to find any explanations of how to do it ...
The simplest thing to do if you have access to only a power-of-two FFT is to zero-pad your data going into the $N=2^p$ FFT and interpolate what comes out.  i think that's what MATLAB does for fft() for non-power-of-two DFT.