An algorithm for analyzing the rhythmic content of acoustic signals of
polyphonic and multitimbral Western music is presented. The analysis
consists of detecting sound onsets, computing an inter-onset interval
(IOI) histogram, and estimating the duration of the shortest notes,
i.e., the quantum period from the histogram. Robustness against tempo
changes has been explicitly built into the system by using short-term
memory for the quantum grid estimation. The results are directly
applicable to computational music processing for making a musically
useful segmentation and computing a musical time base. The proposed
algorithm works causally and a real-time software implementation is
available on-line. The performance of the system was validated for 50
musical excerpts, and the algorithm was found to be capable of finding
the quantum grid from music with a regular rhythm.
