Changing BPM's on mp3's

hi guys. i just downloaded the trial version of audtion 2.0 and want to make sure it can do what i want to do before i purchase it. all i'm trying to do is mix one mp3 into another, kinda like making a mixed tape. anyways, how can i change the bpm's on each song?? i've tried VIEW>DISPLAY TIME FORMAT>EDIT TEMPO......and it looks like i can manually change the bpm's, but when i click OK, and replay the track, its played in it original way, without the bpm change i made.
anyone know how i can change the bpm's on each song?? thanks!

You're going to need to use the STRETCH effect.  The amount you need to stretch it will be based on the ratio of the existing tempo to the desired tempo.

The more you stretch it the more difficult it will be to do it without noticeable artifacts.

thanks zemlin. i'm a dj, and used to working with BPM"s, and i'm new to this recording thing. now in the STRETCH mode, i see the more i stretch it, the higher the RATIO is. is there a way i can modify the speed of the song, by inputting a BPM number? or is this RATIO actually the BPM??

I'm not in front of Audition right now - If I recall the scale in the stretch effect is a percentage.  If the file you have is at 90 BPM and you want it to go to 100 BPM, figure

100*(1-(final_tempo-current_tempo)/current_tempo))

in this case it would be 100*(1-(100-90)/90) or 88.889%

I'm not in front of Audition right now - If I recall the scale in the stretch effect is a percentage.  If the file you have is at 90 BPM and you want it to go to 100 BPM, figure

<edit> - my first reply was wrong - reworking the equation

ok, so what you're saying is, if a song is 90bpm, and i wanna make it 100bpm, i would do the math, and add 12% in that ratio box? ex. - 90 + 12% more = 100.80.
is this the way i should calculate it? =)

When you increase the tempo the file gets shorter, so the percentage will be less than 100.

is there a way we can just input the bpm we want that entire track to be at?

Audition (or any other software) has no way of knowing what the tempo of an audio file is.  There are beat detection techniques, but I'm sure results are mixed with such things.

You need to tell the computer what it needs to do - it isn't going to figure it out for you.

if you load the files in Edit View, right click and choose FILE INFO, you can see what BPM Audition guesses the file is at, and edit the number of beats until it matches what you expect.  Turn on Looping and Time-stretch mode, then add your files into MultiTrack.  Your songs will now stretch to match the session BPM, and will update when you change that.  you can then zoom in to match beats or get precise blends, and everything should be more or less in synch

But wait!

If all you want to use it for is mixing mp3's and adjusting their tempo, is AA really what you need? AA is a professional studio that can do everything from recording and mixing to mastering. You mat find a cheaper or even free package that can do the job if that's all you need