BeaTunes is a commercial software package for Microsoft Windows and Mac OS X, developed and distributed by tagtraum industries incorporated. It originally started as a tool for detecting the BPM in music managed by Apple's iTunes

ITunes

iTunes is a media player computer program, used for playing, downloading, and organizing digital music and video files on desktop computers. It can also manage contents on iPod, iPhone, iPod Touch and iPad....

. Since version 3, beaTunes is not dependent on iTunes anymore and supports Harmonic mixing

Harmonic mixing

Harmonic mixing or key mixing is a DJ's continuous mix between two pre-recorded tracks that are most often either in the same key, or their keys are relative or in a subdominant or dominant relationship with one another....

 and Beatmixing

Beatmixing

Beatmixing is a disk jockey technique of playing two songs at the same time so that the beats of one song occur at the same time as the other.-History:...

 through BPM and key detection. Keys are displayed in either their musical notation or in Open Key Notation.