Techniques disclosed herein are generally related to methods and devices for determining spectral samples for a finite length sequence. Some example methods include, for each time-indexed sample in a data sample sequence comprising a plurality of samples, generating a sample-specific phase value set associated with a respective time index of the sample and a set of predetermined frequencies. Some examples further include, mapping each sample-specific phase value set to a corresponding sample-specific iso-phasor set and calculating an altered iso-phasor set. Some examples include generating a rotated sample value set by unmapping the altered iso-phasor set to obtain real and imaginary components of the sample rotated by the corresponding sample-specific phase value set. Some addition examples include summing selected rotated sample values from each of the sets of rotated sample values to create a spectral sample vector having a spectral sample of the sequence and outputting the spectral sample vector.