Librosa beat track

[Oluwatobiloba Titus Oyekanmi]

Hi 

I was using the librosa.beat.beat_track() function to detect song tempo, but I noticed that it is not accurate. On two occasions, I got a completely different result.

In the first one, the original tempo was 81 but I got 161 from librosa while in the second the original was 69 but I got 136 from librosa

[Brian McFee]

The tempo estimator is making a statistical "best guess", with a default prior centered at 120BPM.  If your tracks are much slower (or much faster), it will likely make mistakes as you've described corresponding to doubling (or halving) of the tempo.

If you happen to know in advance that your tracks are not likely to be in the 120 range, you can modify the default behavior by changing the start_bpm parameter to the beat tracker.