djqualia/RapidEvolution2

"Rapid Evolution 2" is an advanced harmonic music library tool for DJs, designed to be used while you mix. It helps profile your songs by saving important properties, such as the BPM, key, time signature, styles, comments, and more. You can then instantly see which songs are within BPM range, in key harmonically and in similar styles. More importantly, it lets you save comments and information about each individual mix you come up with. It aims to help properly utilizing music knowledge and harmonic mixing theory to create better mixes. Use it to enhance your knowledge of your own music and remember the important details of what you do. The software includes automatic BPM and key detection, as well as tools to determine this information yourself--a BPM tapper and a MIDI keyboard. It also lets you share song and mix information with other DJs.

Associated Google group/forum: https://groups.google.com/forum/#!forum/re2-users

NOTE: This is the source code for the latest version of Rapid Evolution 2 from Mixshare.com.  Please beware: this is very old and ugly code.  It is uploaded for legacy support, so bug fixes can be made to those still using it.  It is recommended to use Rapid Evolution 3 instead, especially if you plan on doing any development.