Well, if the tempos in these tracks are "dead on beat", than you could possibly just select each track and time compress/expand it in simple tempo mode (the one with just the slider). For example if your track was 120 bpm, and you want it to be 100bpm, the tempo factor you would use is 100/120=0.8333 or 83.33%. You could also type in the source bpm, and destination bpm and the factor will be calculated for you. You have to do this seperately for each track, if the tracks are not sycnhronised.
If your tracks often use rubato (wonder off main tempo), you can use Time Morphing mode. to sync up each beat. Beside the text "Tempo" there are two arrows. Click twice the one pointing to the right. This will take you into Time Morphing mode.
Usage of Time Morphing mode is explained well in the manual, page 11,
www.serato.com
In your case, you would first identify a track which you think has the correct tempo, use that track as the "Source" and sync up every other tracks to that one. If none of your tracks are in the desired destination tempo, you will have to choose one track which you will modify to be the right tempo. Than you will procede with syncing up the other tracks to that one.
As you can see it's quite a manual job. There is currently no tool to do this automaticlly. However the accuracy attainable using Time Morphing mode, can make your vocals sound very tight.
