[RWP] changing tempo in reaper.

[Scott Chesworth]

Hi Derek,

Only started exploring this myself last night, so forgive the
inevitable rambling.

For simplicity, let's assume you have a project with a single track of
audio, you know it was recorded to a click, but you want to identify
the original bpm then be able to adjust that at will.

First, we need to ensure that the timebase for this track is set to
time, rather than beats or position or anything else, otherwise when
Reaper adjusts the project tempo it's also going to start tinkering
with the playrate of the audio before we want it to. Set the timebase
for the track in the track menu, or do it for the whole project in
project settings if you prefer.
Next, we need to mark out a bar (or measure on your side of the pond)
for Reaper to be able to figure out the bpm. Place the time selection
neatly around a measures worth of audio with Alt+Shift+[ and
Alt+Shift+]. You can check the selection is neat by looping the
selection, or my new favourite way is to jump to slightly before the
start of the time selection and then use Alt+Space to play missing out
that chunk you've selected. Whichever method you choose, if everything
sounds neat and in time you should be good to go.
Now, we need the actions list because by default this action isn't
bound to a keystroke. Hit F4 to show the actions list, and type tempo
into the filter box you land in. Tab round to the multi-select list
box of choices, and choose "Set project time signiture / tempo from
time selection...". Tab round to "Run/close", and you should be taken
directly to the project settings box. Shift tab once will read you the
new tempo Reaper has decided upon, and it's unlikely to be right on
the money but it will be close if you're selection was accurate.
Accept it, because annoyingly the box is read only at this stage. Now
when you play the project, the click should be roughly right although
it'll probably drift over time. Head back into Project Settings with
Alt+Enter and adjust that tempo to the nearest whole number, and that
should cure the drifting, think Reaper is a bit oversensitive.
The last step is to make sure that your track or project timebase
(whichever you modified earlier) are set back to "Beats (position,
length, rate) so that the audio will sync. Now, if you try adjusting
the project tempo in project settings, the track should sync to each
change perfectly.

FWIW, I've only tried this so far on quite standard tempo 4/4 stuff as
time is of the escence here at the mo, but I'd assume it can work with
other time sigs too because the boxes to specify those aren't read
only at any stage, my guess is that the read only tempo box would
recalculate if you typed in 6/8 or whatever.

Hth
Scott

On 5/22/10, Derek Lane <derek at pdaudio.net> wrote:
> I'm missing how to get audio to sync to tempo.  The autodetect features seem
> to not be working, and checking the box to do this in the project properties
> is doing nothing.  Can someone tell me what I'm missing or provide a step by
> step reference as to how this is to be done?