Audio only project. Please help with tempo change.

There are a lot of ways to skin this particular cat. I think the easiest solution would be just to ignore the tempo, and keep on recording...unless you have MIDI instruments or effects that absolutely need to sync to tempo. If so, there are other options that are a little more complex.
 
Craig

brundlefly
Snap the Now time at 121:01:000. Hit Shift+M for Set Measure Beat at Now, and set Measure 111, Beat 1. The initial tempo will change to 110 without affecting the absolute timing of any clips. Clips will appear to get shorter because the M:B:T scale is the fixed reference in CbB.

Can you explain exactly what's happening in your explanation? I'm interested, but I don't follow.

It's all about ratios of beats per minute. You want 110 beats to go by in the same time (one minute) that 120 beats are currently going by. But that's the same as 110 measures going by in the time of 120 measure (regardless of time signature), and it's easier to snap some number of measures without having to do unnecessary beats/measure math.
 
The +1 measure comes in because measures are are counted from 1, not zero. So when 120 measures have gone by, the Now time is at 121:01, and you want the absolute time at that point to fall on 111:01.
 
So the general rule for any tempo change is to 'Set' the measure at Current Tempo + 1 to Target Tempo + 1.
 
Note that this works for MIDI as well; the MIDI start times and durations will be recalculated to maintain their absolute timing against the new timeline tempo.

+1, Set Measure/Beat at Now is one of the most useful tempo mapping tools there is (manual, but quick), and one of my biggest gripes with other DAWs, since few have anything even close.
 
When working with SM/BAN, due to the "Absolute" issue, it helps me to think of it like a vise (needing a start anchor and end anchor) to "squish" everything proportionally inside of those boundaries. When just changing the start tempo, things start to scoot on you.

I really like brundlefly's solution.  I think I got how it worked, curious to see if I could apply that to other situations,
 
What I would have done is locked all the audio into place, making sure all the tracks were in"absolute" mode and not musical.  If I'm not mistaken you can select all the tracks then contrl-alt and change all the tracks at once,  then you can change the tempo at will.
 
This forum is so cool for learning things.

brundlefly,
 
Thank you!

Another way to achieve this is by slip editing the beginning of each audio take to start at zero then Bounce to clip to make the slip edit permanent. Then you can simply change to the correct tempo without the clips moving around. It basically anchors them to zero. I like using SM/BAN as well. So many ways to do things in Cakewalk. Always interesting to see all the methods of skinning those poor cats.

+1