Knowing the key, DJs can use music theory (such as the Circle of Fifths) to play songs in a harmonically-pleasing order.

The original tONaRT algorithm created by zplane.development had a simple Windows-based demo which could not process multiple audio files at once.

After the Mac OS X version was released, Ali used Mixed In Key to help sequence songs for his Global Underground 31 Taipei album.

Mixed In Key works with Traktor, Serato, Pioneer CDJs, Ableton Live and all other DJ apps.

Other artists include Paul van Dyk, Armin van Buuren, Sebastian Ingrosso, Sasha, Grammy-winning producer Ali "Dubfire" from Deep Dish, Pete Tong from BBC Radio 1, trance producers Blank & Jones, Above & Beyond, High Contrast, Nick Warren, and BT.

[2] While numerous users have identified this as a deterring and unfair form of copy-protection, Mixed In Key employees have responded, claiming that the new requirement has nothing to do with piracy, stating, "an internet connection is needed to analyze new files because Mixed In Key uses very expensive technology that is not available in 'offline' mode.

[6] In 2009, Mixed In Key was nominated for Best New Product of the Year for the 24th Annual International Dance Music Awards, losing only to the iPhone 3G.