Got a guitar track, recorded to metronome, at  90bpm.
 
Need to change the tempo to 80, stretching the audio.
 
How do YOU do this?
 
Suggestions?
 

Re do it. Audio quality will be trashed by changing it's timing. 
Best to decide on your tempo while the song is still MIDI tracks only, then start recording audio. 
You can easily change MIDI tempo via the Tempo icon or using the tempo map, but audio will still remain as it was. Changing the tempo of audio requires using other tools which I forget which, ( audio snap?) but would not even be tempted to use myself. 

Thanks for the response.
 
But::  cannot redo the recording. One of a kind,....
 
I stretched the audio by 1.125%  (90-80=10 10/80=.125)
And then changed the tempo to 80 for the project.
 
This was easy because of the ratios. But is not so easy for other stuff.
 
I have also accomplished this for other projects by stretching/shrinking and the setting the project tempo from the clip. This often results in twice the target tempo. In the current case this resulted in 160bpm tempo.
 
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I use audio snap lots for adapting natural sounds to project tempos.  I recorded lots of firework noises last Thursday eve.   Cloned the tracks and snapped the each set of stereo tracks to 16, 1/8, 1/4 and whole notes. Then I cut the clips and moved them about to have 7 minutes from the original 25.
 
Started adding Zeta rhythms and drums,.... 
 
Do the fireworks still sound like fireworks after the snap/stretching.  Enough to know what they bees.
 
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I am interested in how others stretch clips and change tempos as needed.
 
And: what algorithm is used to stretch?  Anybody know?  Changeable?
 
Audio snap defaults to not the best/slowest conversion. And I change it every time.  Sure would be nice if AS used presets.

The key to getting AS to produce a more natural sound is to bounce down once you've finished.
 
Apologies if you already know this

Duplicate post