A transition between two songs sounds much better, if their beats are in sync. This is only possible, if both songs have the same tempo.
In this tutorial, you learn a quick and reliable way to match the tempo of two songs and align their beats properly
If you create a transition between two songs with different tempi, the result usually does not sound pleasing. In this one minute tutorial for Premiere Pro you learn how to adjust the tempo of the songs such that their beats match perfectly.