Give it a track, artist, BPM and key. Get compatible Camelot keys, a BPM transition range, energy-arc advice, five mixing techniques and five next-track suggestions.
No account, no limit. Nothing you type is stored.
Fill in the track and hit analyze. You'll get five blocks back: harmonic matches, tempo range, where it sits in an arc, how to get in and out of it, and what to play next.
The Playbook has a full chapter on keys, energy and crate work — this tool is the short version.