tuneXplorer!

Mixed In Key is award-winning DJ software that gives you the #1 technique of the world's best DJ's - harmonic mixing.

What started out as a BPM detection tool for DJs, runners and dancers, has become one of the finest iTunes™ library management tools around.

"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. Use it and start evolving! :-) »

It provides you with song information for a massive library of music. It gives you key, bpm, and even values like how danceable or happy a song is.