[phkahler]

This is very much like doing a Fourier Transform without using recursion and the butterflies to reduce the computation. It would be even closer to that if a "moving average" of the right length was used instead of an IIR low-pass filter. This is something I've considered superior for decades but it does take a lot more computation. I guess we're there now ;-)

[arjf]

It only requires more computation if you really need to compute the full FFT with all the bins, in which case the FFT is more efficient... With this approach you only compute the bins you really need, without having to pre-filter your signal, or performing additional computations on the FFT result. Some sliding window FFT methods compute frequency bands independently, but they do require buffering and I really wanted to avoid that.