Loopers become more and more popular due to their growing features and capabilities, not only in live performances but also as a rehearsal tool. These effect units record a phrase and play it back in a loop. The start and stop positions of the recording are typically the player’s start and stop taps on a foot switch. However, if these cues are not entered precisely in time, an annoying, audible gap may occur between the repetitions of the phrase. We propose an algorithm that analyzes the recorded phrase and aligns start and stop positions in order to remove audible gaps. Efficiency, accuracy and robustness are achieved by including the phase information of the onset detection function’s STFT within the beat estimation process. Moreover, the proposed algorithm satisfies the response time required for the live application of beat alignment. We show that robustness is achieved for phrases of sparse rhythmic content for which there is still sufficient information to derive underlying beats.

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