Here’s a quick way to map REAPER‘s tempo track to an existing recording…

Credit due: this writeup–my daily process–is based on posts from several others in REAPER’s (y’know, amazing) user community: https://www.youtube.com/watch?v=1ryz7BfQnzg | https://www.soundonsound.com/techniques/tempo-mapping | https://forums.cockos.com/showthread.php?p=1966295

1. Set a couple of things up in REAPER

  • Get the SWS Extensions for REAPER
  • Set up a keyboard shortcut for the Action “SWS/BR: Move closest grid line to mouse cursor (perform until shortcut released)”
    • Actions menu | Show action list
    • type the action name into the Filter box
    • click the action in the list
    • Below, in the Shortcuts for selected action area, click “Add”
    • type the key you want to run this Action (I’m using comma: “,” )
    • Hit Close.

2. Map Those Beats

  • Pull your recorded track into REAPER.
  • Listen and pick an approximate baseline tempo (you could use these scripts, but I feel like it’s faster to just tap into a metronome).
  • Add a tempo marker at the beginning of the track in this baseline tempo.
  • Set gridlines to something sensible that you want to map — I mean, quarter notes, probably. (Right-click on REAPER’s Grid Lines button, then hit the “…line spacing” dropdown.
  • Play the track; pause and hold the mouse over the beat in the waveform, then hit your keyboard shortcut to snap gridlines into place. aren’t lined up with the track.

I’m often able to do this only for downbeats (or even less often for tracks recorded with click), but it’s crazy fast and flexible even if I have to do all the beats within a measure. Part of the magic of this SWS action is that it will preserve the position of later markers, so you can tweak beats within a measure without ruining everything down the line.

Like magic. Happy beatmapping!