Please help me understand sliding stretch!

Hello, I’ve been using Audacity for a while for simple tasks like creating playlists, etc. But I would like to create a track that gradually increases the tempo (not pitch) throughout the length of a song. This is for a spin class where we will gradually increase the cadence from, let’s say 60 bpm to 90 bpm over a 3.5 minute song. From the documentation, sliding stretch does exactly what I want, but when I apply the effect it immediately starts accelerating the song at a fever pitch and ends at a tempo that is not even recognizable as a song. I obviously don’t understand how this effect works, can someone help please? Thanks, cob
Sliding Stretch WTF.PNG

Start off by reading this manual page:


So what parameters were you using?

I think the trick to using this effect is to first look at Effect > Change Tempo. On that screen you can enter 60bpm and 90bpm, and it will show you that your % change is 50%. So you are going to start with 3 1/2 minutes of existing audio. Select your 3 1/2 minutes, then Effect > Sliding Stretch, then keep all parameters at zero, except for the Final Tempo Change of 50%.

If you need to end up with 3 1/2 minutes of audio, you are going to need a longer recording to start with. So your average resulting bpm is going to be 75bpm (60+90/2). You can figure this out easily: Total # of beats = 3.5min * 75bpm = x min * 60bpm; or x = 3.5min*75/60.

I hope this helps. :smiley: