For two tracks the Director chooses: where in each track to mix, how many bars the mix lasts, the shape of the fade, the bass, mid and high moves of each deck's equaliser, and small loudness corrections section by section.
It studies both tracks (their bass, mids, highs, drums and sections), tries many blends in a simulation, and keeps the one that sounds smoothest by its own measures. It explains its choice in words in the Lab.
Tip. It is a good first plan, not the last word. Your ears decide. Change what you do not like and rate the result.
Keeping a mix or a plan: the app keeps the last mix you planned and the last set you planned, and offers them when it opens again (Load last mix, in the side panel of the Library and in the Transition Lab; Load last set plan, in SET DIRECTOR and the Set's Plan pane; and the same in the File menu). File ▸ Save Mix… saves the mix on the decks as a .nfx file, named after its two tracks. File ▸ Save Set Plan… saves a planned set as a .nfxp file, named after the Set. Once a set plan is saved to a .nfxp file, or opened from one, every change to the plan (a mix you keep or plan again, a mix you refine) is saved back to that file automatically, with your verdicts on the mixes; the Plan pane says which file it is saving to. File ▸ Load Mix or Set Plan… (or opening the file) puts it back as it was planned: for a mix, both tracks go on the decks the way round it was planned; for a set, the plan appears in SET DIRECTOR and the Plan pane. The Director does not plan again. A file holds the plan and the names of the tracks, not the music, so the tracks must be in your library. These are binary documents that only A/B TEKNIQ can read: a file that was edited outside the app, cut short or damaged is refused with a message instead of being opened.
Bass cuts: in a long Club, Studio or Radio blend with a bass swap, where the arriving track is mostly beats before the swap, the Director can cut the leaving track's bass in quick stabs in the last bar before the hand-over (on beats 1, 2 and 3, then on the half beat), and the swap itself is the last cut. The mids and highs blend smoothly over a long stretch, and the leaving track's snare and hats are well down before the cuts so they do not play over the new drums. It is part of the Director effects switch, and the plan lists it as bass cuts.