Skillnicker instead. I took the engineering route instead. And here we are.
When you want to mix two songs togheter they needed to be in the same tempo, therefore we marked our records with the number of BPMs a certain song had. We calculated in the beginning by measuring the length of 16 beats with a stop watch and look into a table. After a while there were programmes where one just could tap the space bar and get a decent result. Here is such a program in Clojure.
The intresting part of the program is the minimal state, it's just the last time we got a key press in the frame. I will add a Kalman-filter to it soon, giving it a state of a hefty two or three variables.