Tony Yarusso's Blog

So, here's a slightly odd thought I was having: I'd like to be able to take songs (ie, off of CDs), and change their tempo, preferably without having to do much work, so that I can reasonably do fairly significant batches of this. So, there are a few steps to this, and I'm wondering if anyone has advice for any of them.

1. I need to find out the current tempo in some way, to know how much it needs to change to meet a particular target. So far the only thing I've found for doing this is the "tap this button when you hear the beat" feature in Jokosher. This gets the job done (and is actually pretty nifty in its own right), but is susceptible to human error and a bit clumsy/time-consuming for many files, so if there was some magic way for a program to detect it that would be really nice.
2. I need to actually do the actual speed adjustment. Audacity seems to do this pretty well, so this may be the easiest step actually.
3. I need to adjust the pitch to bring it back to where it was before step 2, so I don't get a bunch of "Alvin and the Chipmunks" covers of my music instead. I found some plugins for Audacity that claim to accomplish this in the swh-plugins package, but the quality of the result is very sub-optimal. There seem to be a bunch of other such plugins packages, so maybe one of them contains something better.

Now, in a perfect world, I would run a command that took as arguments the target tempo, input directory, and output directory, and just did its thing. That's probably more complicated to code than I can reasonably expect, but hey, maybe I'll get lucky - anyone know of such a thing?