You know maybe forty good pairings in a two-thousand-track library. The engine knows them all. Prep mode is mimetic discovery: CueDJ plays your library back at you in combinations you haven't tried, you audition the seams, keep what works, and walk into the gig with a plan you couldn't have built by hand.
Drop any track in as the seed and the engine chains nearest neighbors into a draft: every link scored, every key relation shown. Reshuffle until something surprises you. It will.
Then audition: render any seam at full or double speed, swap a link, lock the keepers.
↑ drafts reshuffle as the engine walks different paths through the same library
BPM, key, energy, phrase grid, spectral profile. Computed once, offline, for everything you own. Sort and filter by any of it. Your library stops being a folder and starts being a map.
Select any track and see its neighborhood: every compatible exit ranked by score, with the reason printed. The question you ask a hundred times a week, answered in one view.
Locked drafts export as tracklists and transition plans: text and CSV today; rekordbox cue export is high on the early-access roadmap. The plan is yours; play it loose or play it tight.
The seams you audition in Prep are the exact seams Listen renders and Perform suggests: one engine, one scoring function, three surfaces. What you learn in one mode transfers to all of them.
A score is a measurement, not taste. The engine will hand you technically perfect pairings that are emotionally wrong. That judgment stays your job, and Prep mode is built so exercising it is fast.