What hard start on bar 1 does

Hard start on bar 1 removes any silence, fade-in or pre-roll from the front of the rendered audio so that the first beat sits at 0:00. It is on by default in the DJ mix edit panel. Everything that depends on timing, the beat grid, the cue points and the bar counts for the intro and drop, is measured from that point.

Why it matters

Music models often leave a short gap, a breath of room tone, or a fade before the first kick. On a CDJ or in DJ software that gap means the track starts with nothing, the beat grid is offset by however long the gap was, and the cue point you expected at bar 17 is actually at bar 17 plus the gap. A hard start fixes all three at once. It is also what makes a track usable from a cold cue: press play and the kick hits.

How Club Ready Music does it

Before loudness measurement, a silence-removal filter scans from the start of the file and discards everything before the first sample whose peak exceeds −45 dBFS. The threshold is low enough that a quiet but intentional opening is preserved, and high enough that room noise, encoder padding and a trailing fade from the model's own intro are removed. The trim runs before the loudness measurement so the measured length and the final length agree.

In the style prompt Club Ready Music also asks the model for a "hard start on beat one with no pre-roll", so most renders need little trimming. The filter is there for the ones that do.

What depends on it

• Beat grid. The Serato grid embedded in the MP3 and the tempo marker in the rekordbox XML are anchored at 0:00 with your BPM. If the first beat were late, every downbeat marker would be wrong by the same offset.
• Cue points. Intro end, first drop and outro start are computed as bars times seconds-per-bar from the start of the file. They are only correct if the file starts on the beat.
• Vocal gate. The intro window for muting vocals is measured from zero.
• Bass fade. The last-eight-bars fade is measured from the trimmed length, so the trim is applied first and the fade computed from the result.

When to turn it off

Rarely. If you want an atmospheric opening that begins below −45 dBFS, or a deliberate half-bar of silence for a specific edit, untick it. Be aware that the grid and cues will then be offset by whatever the model left at the front.

What it does not do

It does not quantise the audio to a grid, time-stretch, or detect the beat. It removes leading silence. If the model placed the first kick on an off-beat, that is a prompt problem, not a trim problem, and the second take is often different.