Digital DJ Tips decided to test the Key Lock feature of iOS DJ apps. This is an important feature, which keeps the pitch normal when you sync tracks of different tempos. All apps seem to handle it a little bit differently. Traktor's results are particularly bad.
Quick test of keylock functionality and audio on iOS apps - specifically DJ apps. I used "Touch Me" by Rui da Silva as the test track, as it features kicks, snares, vocals and synths in the section I used.
I played the same section of the track on all the apps in the test, at -16% with Key Lock enabled on a 3rd Generation iPad running the latest version of iOS (6.1.3) and the latest version of all apps involved (as of 25.03.2013).
The uncompressed audio can be heard here: http://soundcloud.com/djhombre/sets/ios-key-lock-test
The apps used were Capo, Traktor DJ, DJ Player (NB: on the audio in the video for this app is in Mono - my mistake...on Soundcloud I re-recorded with the correct in-app setting for stereo output), CrossDJ, djay, Touch The Wave (TTW).
CrossDJ was recently updated with Keylock, and made some pretty bold claims about the quality of their algorithm used. Digital DJ Tips took up the challenge, which was the inspiration for this test. You can read a full article over on Digital DJ Tips that takes a deep look at their claims. This is extremely well done. Not only do they call them on their marketing buzz, but they get into the technical backend of all these apps.
CrossDJ certainly performs much better than Traktor! It is celebrating its 1 Year Anniversary, with a 90%-off sale this weekend only.