Do you want to change the tempo as displayed in the ruler, or actually stretch/squash the song to match a specific tempo?
To change the ruler tempo as displayed for just this file, open the file in the Editor, open the Properties Panel (Window > Properties if it's not already open) and twirl-down the "Advanced" menu at the bottom of the panel. You can change the Tempo and Time Signature here and it will update the ruler if in Bars and Beats mode.
To stretch the audio by some amount, use the Time Stretch effect located under Effects > Time and Pitch > Stretch and Pitch (process)... If you know the original tempo of the file and the tempo you desire, there is a simpel formula to help you determine what percentage to stretch:
Percentage to Stretch = (Desired Tempo x 100) / Original Tempo.
You can also use the Stretch effect to stretch or squash a file to a specific duration or number of samples if you wish to perfectly match the duration of other clips.
Thank you for your prompt answer. This partly answers my question. Let me expand more.........
I haven't used AA since edition 2 and have since transferred my work over to Logic Pro since moving over to Mac.
I create CD's for Dressage to Music Competitions. I need to compile a 'song' from a number of different audio tracks to match the horse's change of paces throughout a dressage test, which are matched to the horse's BPM as it passes through walk, trot and canter. As such I need to change the Music's BPM several times throughout a continuos 'song'.
In AA 2 I had to chop each track (lots of orange lines, I seem to remember) and then change the BPM for each of the tracks and then paste each of them with a crossfade.
In Logic, I simply 'rubber band' the tempo as I go along, but I can only do this once the audio track has been converted to an Apple Loop or Acid Wav.
Even with your description I am struggling to see how I achieve this in AA 4.
Will you please expand your answer to take into account my needs highlighted above.
If I can achieve what I want without having to create loops out of the audio tracks I wish to use and alter the tempo with ease then I can see myself coming back to AA.
I understand your question better now. Thanks for the full description.
Audition has not previously supported a dynamic tempo track, although it is a feature we're considering for a future release. I THINK this may be the sort of tool you'd find valuable for this sort of work, if I understand you correctly. If you could just drop markers along a single file (or single timeline in Multitrack) then stretch each of those regions to a new tempo, would that accomplish what you're after?
Thank you again for the prompt response.
Using the markers on a single track works extremely well. My only gripe now is that with the Time Stretch tool I have to work in 'Stretch' percentages and carry out time-consuming calculations. Wouldn't it be much simpler to have a Tempo option in BPM that I could adjust the stretch to. This would speed my workflow up tremendously or am I missing something?
I think that's a great idea, and one that I'll make sure is included in the notes for additional stretch/tempo feature work. I think it would require more backend for proper BPM analysis, but wouldn't be too difficult.
I am sure that such a function would be well received and I can't imagine why somebody hasn't thought of it before. Without it, I am unlikely to buy this edition for the delays involved in getting to where I want to be. Maybe your developers will give serious consideration to including it in the following version and maybe someone will send me a free copy for the idea :-)