What happens when you add a track
Before a track is ready to mix, DJ software needs to know a few things about it: the tempo, where every beat falls, the key, and how hard it pushes. Here's what you'll see in Mix//Sync while that happens, what to look out for, and what to do when a track comes out wrong.
Tempo
In Mix//Sync, a file whose tags already carry a tempo lands on a deck at that tempo straight away, and the number is refined when the analysis finishes. A track with no tempo anywhere shows "analyzing…" until then. A small "grid?" mark beside the BPM means the grid is worth a look. Click it to open the grid tools, where you can set the tempo.
The common mistake in any DJ software is a tempo read at half or double its real speed, 64 where the track is really 128. Music played by a live drummer is the hard case: it drifts, so no single number fits it.
The beat grid
The tempo isn't enough on its own. Each track also needs a marker on every beat: the beat grid. Sync and loops work from it. Every track in Mix//Sync gets one, with bar 1 marked, and a grid you set in Rekordbox is kept as it is.
Key
Mix//Sync shows each key as a Camelot code, on the deck and in your library. Treat it as a guide. The usual mistake in any key reading is confusing a minor key with its relative major, because the two share the same notes, and a track that changes key, or barely has a melody, can come back with a guess.
Energy
Energy is how hard a record pushes. It's a rough guide rather than a fact about the music, and two records at the same energy can feel very different. You'll see it in the word on each Fits with card under the decks, Rises, Peaks, Holds or Eases, comparing that record with the one on that deck. A Build the mix draft uses the same words.
Where and when it happens
All of this runs in your browser, on your own computer. Your files aren't uploaded anywhere. Mix//Sync reads each file's tags first, then works through your library in the background, and the library shows its progress, for example "Analyzing 120 of 900…". A track you load onto a deck is analyzed right away. In a session with a partner, the rest of your library waits until later, so the background work doesn't disturb your mix.
When the analysis is wrong
No analyzer is right about every record. When a grid sits off the kicks or a tempo reads half or double, fix it on the deck: Fix a beat grid shows how. A later analysis never overwrites a fix you made by hand.
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