Fast Fourier transform
Almost twenty-four years later, Don Pearson and producer Dan Healy solved this problem by employing a B&amp;K 2032 Fast Fourier transform (FFT) digital spectrum analyzer to measure the delay in time between the different microphones, using the track of bassist Phil Lesh as the time centerpiece. The delay times were fed into a TC1280 stereo digital delay, which, along with careful mixing, resulted in a nearly perfect stereo image.