Your BPM is lying to you

Beat detection reports the tempo of the grid. It does not report the tempo of the experience. Those diverge constantly, and the gap is where most bad transitions live.

The doubling problem

A record at 140 with a half-time kick feels like 70. A record at 70 with busy hats feels like 140. Detection software picks whichever reading has the strongest periodicity, which means it will happily report the same record two different ways depending on the mix.

Swing eats tempo

Heavily swung records feel slower than their number because the ear tracks the lag, not the grid. Two records at the same reported tempo with opposing swing will never sit comfortably together no matter how well you beatmatch them.

IF THE NUMBERS MATCH AND IT STILL FEELS WRONG — check the swing before you check the key.

This is why the rhythm dimension exists as its own score. Tempo is metadata. Rhythm is the thing you are actually matching.