So I have a vocal that has been recorded almost perfectly to a rough demo click track. The corresponding instrumental track for that vocal, however, (i.e. the band's final instrumental recording) was recorded on a separate session, and NOT to a click track. The band is happy with the tempo of the instrumental track the way it is, dynamic, live, organic and unquantized. The singer is happy with his performance in terms of quality and expression. All they want is for me to make the vocal tracks fit the backing tracks rhythmically, following all tempo variations. Now I know Reaper's algos for timestretching are good in terms of maintaining quality and avoiding artifacts (maybe elastique soloist + tonal-optimized?), but can someone point me to the most practical workflow for doing this? The most common scenario are clear tempo slopes (the band starts playing a section at around 90 bpm and ends it 20 bpm faster, for example). Is there a way to just push an audio media item to time stretch it on a slope like that (logarithmically?)? That could get me at least in the ballpark. I could try stretch markers, but that would take forever for a whole album... and I'm not sure I'd get it right.

 

You can try automating the tempo, not sure in reaper tho,but i've done it before in FL Where ive used different vocals at different tempos.Or you can try warp timing feature in newtone in FL.

 

The whole album, like that? And they gradually change the tempo over a section's length?
Tell them they need to re-record the vocals.
Whoever was producing this album messed up. Recordings should not go that way.
Not your fault, not something you can fix. Tell them all they need to re-record the vocals over an instrumental.

 

I know of one thing that might help you. Never tried it myself tho. In Studio One, you can set the audio file's tempo, you can set the audio track to stretch the files to the song's tempo and you can gradually automate the song's tempo.
All three combined should give you something close to what you want in theory.
But honestly by fixing other people's fuckups in this manner you're creating a bad precedent for them. Next time they'll fuck up even more, cause they know you can fix it. At least reprimand them and make it seem like fixing it was a very non-trivial task. Mention that you had to consult other professionals in your sphere : )

 

Solved: tempo automation + change media item timebase to "beats (auto-stretch at tempo changes)". Gotta love Reaper! Thank you everyone who chimed in.