Respective pitch values are estimated for an audio signal. Candidate harmonic segments of the audio signal are identified from the estimated pitch values. Respective levels of harmonic content in the candidate harmonic segments are determined. An associated classification record is generated for each of the candidate harmonic segments based on a harmonic content predicate defining at least one condition on the harmonic content levels. An associated classification record also may be generated for each of the audio signal segments classified into a harmonic segment class based on a classification predicate defining at least one condition on the estimated pitch values. The classification records that are associated with ones of the harmonic segments satisfying the classification predicate include an assignment to a speech segment class. The classification records that are associated with ones of the harmonic segments failing to satisfy the classification predicate include an assignment to a music segment class.