What happens when the Master Deck's beatgrid is wrong.

What happens when the Master Deck’s beatgrid is wrong

What it means for the master to be wrong

“The master’s grid is wrong” is not a single fault. It is a name for several different errors, each disrupting the mix differently.

• Offset. The grid is complete, but shifted relative to the hits. The beats land between kicks.
• Scale. There are twice or half as many beats as there should be, or the spacing between beats is incorrect. The grid ends up where the music has no pulse.
• Variable tempo. The track changes tempo, and a single fixed grid cannot follow it.

A fourth problem joins these three. It is a workflow problem rather than an analysis error: the error is not detected because nobody checks the grid before synchronising.

Why the error spreads

This is the heart of the matter. The rekordbox documentation defines BEAT SYNC as automatic synchronisation of the playing track’s BPM and beat positions with those of the sync master’s track. Notice the second half: it synchronises position as well as speed.

Traktor goes a step further in a particularly revealing sentence explaining why BeatSync does not allow pitch bending of phase: phase is locked according to the grid rather than the beat. With TempoSync, by contrast, you can pitch-bend phase while tracks play.

Put that into practice: when you activate Sync on a deck, it is not aligning with the kick you hear. It is aligning with the master’s grid. If that grid is half a beat off, the following deck will be half a beat off too. The software will also consider that correct and keep it there.

An important accuracy note: the manuals do not contain a literal sentence such as “if the master’s grid is wrong, everything else breaks”. They document the two premises: (a) Sync takes BPM and beat position from the master, and (b) the grid may be wrong, offset or scaled, and can be corrected and locked. The consequence, the spread of the error, is the operational conclusion from those premises. Traktor comes close to stating it when it warns that grids must be correctly set for BeatSync to work.

The three typical symptoms

Symptom 1: the BPM matches, but it still sounds wrong. This is the signature of an offset. If the numbers match but the kick sounds confused or “floating”, suspect offset rather than tempo.

Symptom 2: pressing Sync makes the deck jump somewhere unexpected. Phase is repositioned on the grid. If that grid is offset, the jump leaves the deck away from the audible hits.

Symptom 3: Sync slips on its own. The grid may be incorrectly scaled. The rekordbox manual documents the correction buttons’ exact geometric effect: doubling the BPM halves the distance between beatgrid lines, and dividing it doubles that distance. When analysis produces double the BPM, there are twice as many positions as exist in the music, and Sync works with an invented grid.

Traktor documents another nuance: within a tempo zone between two Grid Markers, tempo cannot be adjusted continuously, only to values compatible with the zone’s length. An incorrectly built grid therefore does more than displace phase; it can restrict what you can correct later.

How to check it

Before touching anything, isolate the problem:

1. Turn off Sync and play only the master track. If it sounds wrong by itself, the problem is the track rather than Sync.
2. Look at the grid in the enlarged view. In rekordbox, user-modified grids are drawn in blue rather than white, so you can tell at a glance whether a track has a manual grid or one generated by analysis.
3. Use the metronome. The rekordbox documentation describes the metronome sound starting with the playing track, synchronised to the beatgrid. Traktor has an equivalent with another name: Beat Tick. In Internal Mixer mode, the manual explains that it is heard only through the headphone channel, exactly what you need to keep it out of the booth output.
4. Try the other deck. Load the same track with a grid you know is correct and synchronise. If the problem persists but changes its form, the master is the suspect.

How to fix it

The fix is made in the master rather than the following deck. Correcting the follower’s grid to compensate for the master’s error is a patch that breaks as soon as you change tracks.

In rekordbox, the documented procedure uses the [GRID] panel in EXPORT mode or [GRID/PHRASE EDIT] in PERFORMANCE, with fine adjustments of 1 ms in both and also 3 ms in PERFORMANCE, plus the option to set the nearest position to [1.1Bars]. Scale errors have specific double and divide BPM buttons with the geometric effect already described. Traktor offers an equivalent workflow on the Advanced Panel’s GRID page, with TAP, Reset BPM and Reset GRID.

Two warnings save trouble:

• Work during preparation, rather than live. In EXPORT mode, rekordbox documents that you cannot adjust the beatgrid while the computer is connected to PRO DJ LINK-compatible DJ equipment. In certain booth setups, correction is therefore simply unavailable.
• Lock the work when it is right. The rekordbox manual warns that reanalysing tracks overwrites the manually adjusted grid with the reanalysed one. Analysis Lock prevents this by blocking reanalysis and grid editing. Traktor describes the same idea with its analysis-lock button.

Common mistakes

“If the BPM matches, the grid is right.” False. A half-beat offset does not change the BPM and ruins the mix. Offset and scale are independent errors.

“I synchronise, then correct it with pitch.” It may not let you: in Traktor, a deck synchronised to a Tempo Master cannot have its tempo adjusted manually. Even where it allows this, correcting phase by changing tempo is an unstable patch.

“I correct the following deck, and that is it.” That only hides the problem in that particular mix. The next track you synchronise with the same master inherits the error again.

“I fix it live in the grid panel.” It depends on the setup: with PRO DJ LINK in EXPORT, rekordbox does not allow adjustment. Live grid editing is also an unnecessary risk.

“There is no need to lock it; I already adjusted it.” Later reanalysis overwrites the adjusted grid. Without locking it, your work has an expiry date.

If the master is correct but nothing lines up, the next suspect is usually pitch: What Master Tempo / Key Lock is and what it does to the sound.