Harmonic mixing has become an integral part of a lot of digital DJs arsenals, reflected by the presence of key detection algorithms in a variety of softwares. We last stood just three entrants against each other in a harmonic showdown in 2012, but this year we've got 12 different algorithms competing in our key detection comparison. How does Traktor Pro fare versus Traktor DJ? Is Rekordbox reliable? Is the new Mixed In Key worth an upgrade?