command-line tool to calculate tempo of audio

 The bpm-tools commands are used to automatically calculate the tempo
 (in beats-per-minute) of music, optionally displaying an analysis and
 adding it to file 'tags'. The data from these tags can be especially
 useful for navigating a music library in DJ software such as xwax(1).
 .
 The bpm command implements the algorithm on raw data, but the most
 commonly used command is bpm-tag to tag the file with the tempo in bpm.
 The bpm-graph command will produce a plot of the results of the
 autocorrelation.