However, some modern DJ software can change pitch and tempo independently using time-stretching and pitch-shifting, allowing harmonic mixing.
In 1978, the Technics SL-1200MK2 turntable was released, whose comfortable and precise sliding pitch control and high torque direct drive motor made beat-matching easier and it became the standard among DJs.
More recently, software with similar capabilities has been developed to allow manipulation of digital audio files stored on computers using turntables with special vinyl records (e.g.
Other software including algorithmic beat-matching is Ableton Live, which allows for realtime music manipulation and deconstruction.
Freeware software such as Rapid Evolution can detect the beats per minute and determine the percent BPM difference between songs.