wormjar making an anyliser with a low CPU drain is possible, but like with most things there's a tradeoff. In this case perormance is inversly proportional to how accurate the display will be.. Most musicians want to know exactly how the singal is distributed in the frequency domain of the sample, and will therefore be prepared to take a small hit in performance. It'd be good if DSP coders would add FFT size parameters in their plugins though.