Auto Beat Match
Auto Beat Match is a mode that analyzes all sounds for tempo, beat and key data.  It attempts to detect the beats in any supported audio file.   The drawback to automatic beat match mode is that it takes longer to detect tempos and key information (initial loads are two times longer although subsequent loads will be cached and load faster).

If you click the Auto Beat Match button on the Project Details Tab after loading in some songs or sounds, it will detect the tempos and keys of loaded sounds and adjust them to match the project tempo.

Alternatively, you can toggle Auto Beat Match mode by choosing Automatically Beat Match New Sounds from the Mix menu.

For tips on beat matching, see How To Beat Match Songs or How To Fix Songs With Drifting Tempos.