Harmonic mixing

Harmonic mixing or key mixing (also referred to as mixing in key) 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.

The primary goal of harmonic mixing is to create a smooth transition between songs. Songs in the same key do not generate a dissonant tone when mixed. This technique enables DJs to create a harmonious and consonant mashup with any music genre.

The Camelot wheel can be used for harmonic mixing. It is based on the circle of fifths.

Traditional methods
A commonly known method of using harmonic mixing is to detect the key signature of every music file in the DJ collection by using a piano. The key signature can be used to create harmonic mash-ups with other tracks in the same key. Also considered compatible with the key signature in question are its related subdominant and dominant keys, as well as its relative major (or minor, as the case may be) key.