Apparatus having corresponding methods and computer-readable media comprises a receiver to receive a wireless stereo frequency-modulation (FM) signal comprising a plurality of spectral signal components including a first tone and one or more frequency bands; one or more tone generators each to generate a respective second tone based on a respective one of the frequency bands; a plurality of phase circuits each to measure a phase of a respective one of the first and second tones; and a difference element to determine a phase difference between two of the phases.