Beat matching for two audio streams extracts beats from each, computes a conversion ratio from one stream to the other stream by an initial beat alignment plus a stability-maintaining beat alignment. A variable resampling converter or time scale modifier adjusts one stream to align beats with those of the other (reference) stream. Thus for cross-fading two music streams the beats of the fading-in stream can be matched to those of the fading-out stream for a seamless transition.