Pitch & Key
Camelot Wheel
Pick the key of your current track. Every key that mixes cleanly with it lights up — same number, or one step either way.
The math
compatible(nX) = same number, other letter · n−1 same letter · n+1 same letter (wrapping 12→1)
The wheel arranges all 24 keys so that neighbors share the most notes. 8A (A minor) and 8B (C major) contain the identical seven notes — they're relative keys. 8A and 9A (E minor) differ by exactly one note. Any move of one step keeps six or seven of seven notes in common, which is why the transition sounds seamless.
In practice
Same-number letter swaps (8A→8B) shift mood between minor and major without changing a single note — the cheapest emotional gear-change in DJing. Going +1 (8A→9A) lifts energy; −1 settles it. Two rule-breaks worth knowing: +2 (8A→10A) works as a deliberate energy jump when the outgoing track is mostly percussion, and +7 semitones — the "energy boost" mix — lands if you time it to a breakdown. Key-detection software is wrong maybe one track in ten, so trust your ears over the tag when a "compatible" blend clashes.