Key & harmony
Dissonance
Dissonance is the unsettled sound of notes that do not agree; consonance is the settled sound of notes that do. Neither is a fault — a record with no dissonance anywhere has nothing to resolve.
In practice
Dissonance inside a record resolves. Dissonance you create between two records does not — it just sits there.
That is the whole practical rule. When a pairing sounds wrong, you are not hearing "bad music", you are hearing an unresolved interval with no arrangement behind it to move it anywhere. The fixes are all about removing one side of the clash rather than balancing it: swap the bass, cut the mids on the outgoing record, or shorten the overlap so the two harmonies are never both present for long.
Resolves
Dissonance inside a track
Sits
Dissonance between two
Remove
The fix, not balance
Where these come from: Harmonic behaviour and mixing practice. The measured rate at which real DJs make in-key moves is on the harmonic mixing page. For what we can measure, see the system for avoiding it.
Why it matters
It is the mechanism under everything harmonic mixing is trying to manage. When two records clash, what you are hearing is dissonance introduced by accident between two arrangements that were each consonant on their own, and the reason it is so unpleasant is that nothing in the music is going to resolve it.
The distinction that matters is intent. Dissonance a producer put there gets resolved a bar later, and the tension is the point. Dissonance you created by overlapping two keys just sits there for the length of the blend, which is why the same interval can be thrilling inside a track and unbearable across two.
Frequently asked
Is dissonance always bad?+
No — inside a track it is what creates tension and makes a resolution land. It is only a problem when you create it between two records, because then nothing resolves it.
What is consonance?+
The opposite: notes that agree and sound settled. Octaves and fifths are the most consonant intervals, which is why the wheel is built on them.
How do I fix a clashing blend?+
Remove one side rather than balancing them — bass swap, cut the mids on the outgoing track, or shorten the overlap so both harmonies are never present for long.
Related terms
Tritone
A tritone is six semitones — exactly half an octave, and the most dissonant interval in Western music. Two keys a tritone apart sit opposite each other on the wheel and share the fewest notes.
Harmonic mixing
Harmonic mixing means choosing the next track by key as well as tempo — staying on the same Camelot code, moving one step around the wheel, or swapping between the major and minor of the same number.
Chord
A chord is three or more notes sounding together. Which notes they are decides whether a passage reads as major or minor, and the set of chords a track uses is what a key detector is trying to infer.
Absolute pitch
Absolute pitch is the ability to name a note without a reference. It is rare, largely fixed by early childhood, and — unlike almost every other musical skill — it is not what DJing actually requires.