CONVERT A SONG WITH VARIABLE BPM TO A FIXED BPM

[Angel Alexis Bonilla Gonzalez]

Hello MY DOUBT IS IF IT IS POSSIBLE TO CONVERT A SONG WITH VARIABLE BPM TO A FIXED BPM. As the case may be, I have a song that is at times 120 BPM, but then increases to 124 BPM. Will it be possible with Python or some other tool to convert it to a fixed BPM?

Thank you very much for your time

[Brian McFee]

Yes, this should be doable with a few tools.

librosa has a time-varying tempo estimator, so you should be able to measure this reasonably well.

To "straighten" the metrical grid, you can use either pytsmod or (py)rubberband.  These packages both provide tools that let you map anchor point times to desired output times, see eg:

• https://pytsmod.readthedocs.io/en/latest/pytsmod.html - all algorithms support dynamic anchor points
  
• https://pyrubberband.readthedocs.io/en/stable/generated/pyrubberband.pyrb.timemap_stretch.html

It'll be on you to determine how exactly you want to construct that mapping from the tempo estimates.  I haven't compared the two packages head-to-head, but the interfaces are similar enough that it should be easy enough for you to do.