Key lock ships enabled by default in most DJ software and CDJ hardware. In a live context, that default is fine. If a pitch-correction artefact appears briefly mid-blend, nobody in the room notices. In a recording, those artefacts are there permanently, baked into every track that was processed with a tempo offset applied. This article explains what key lock actually does, how the three major platforms differ in algorithm quality, and when turning it off is the right call for your recording.

If you're also thinking about harmonic compatibility in your sets, How to Mix in Key covers that side of the equation. This article is about what key lock costs you in the recorded file.

What Key Lock Actually Does

Key lock (called Master Tempo on Pioneer CDJ and XDJ hardware, Keylock in Traktor) is a real-time DSP algorithm that preserves a track's original musical pitch when its tempo is adjusted. Without it, dropping a track's tempo by 6% translates to roughly a semitone of pitch loss, which is enough to put it noticeably out of key with whatever you're blending into. The algorithm corrects for this by time-stretching the audio signal in real time.

The mixer plays no part in pitch correction. Whether you're using Serato DJ Pro, Traktor, or rekordbox in laptop mode, the key lock processing happens in the software before audio reaches the mixer. On standalone CDJ and XDJ setups, the player hardware handles it instead. By the time audio arrives at the mixer input, the processing decision is already done.

In a Recording, the Artefacts Stay

Time-stretching algorithms introduce artefacts. At small tempo offsets (±2 to 3 BPM in a single-genre set) the artefact is below what most listeners would identify. Push the offset further and it becomes audible. Percussion is where it shows first. Hi-hats and snares develop a slightly unnatural texture. Depending on the algorithm, that registers as a watery quality, or something more metallic.

In a live mix, this is transient. The blend completes, the track settles, the processing moves on. In a recording, any track you played with a tempo offset and key lock active has that processing permanently embedded in the audio. You cannot remove it at the mastering stage. What went into the file is what comes back out.

This makes the key lock decision more significant for recording-focused DJs than for those playing live. If you're producing a promo mix, a podcast episode, or an archive recording, you're committing those processing choices permanently.

How the Platforms Compare

The most thorough published comparison of key lock algorithm quality is a 2014 DJ TechTools test, now over a decade old, testing software that predates current major versions by at least two releases. No comparable current-version comparison has been published since. The findings remain the baseline, which says something about how infrequently this has been tested.

Serato DJ Pro

Serato's Key Lock runs on the Pitch n Time algorithm, a professional Pro Tools plugin from 1998 that was built for studio pitch and time correction. The company describes it as "a high quality time-stretching and pitch-shifting technology that premiered in 1998 to revolutionise the way we work with audio in the studio environment." Serato was rated "far and away the winner" in the 2014 test across the three platforms, with better performance when slowing tracks down. That studio-grade lineage is why. The algorithm is bundled in Serato DJ Pro. The exact quality tier available in the current 4.x release hasn't been publicly documented in comparable detail since the original plugin era.

Traktor Pro

The 2014 test found Traktor Pro 2 usable at smaller offsets but with a distinct ceiling: the keylock engine "drops off a cliff" at around ±30% tempo adjustment. No independent test of Traktor Pro 3 (released 2018) or Pro 4 has been published. Research for this article found no documented keylock algorithm changes in Native Instruments' release notes across Pro 3 versions. For practical recording use (which rarely involves ±30% offsets), Traktor's keylock is workable; the gap with Serato at normal offset ranges is smaller than the extreme-offset test suggests.

rekordbox and Master Tempo

Pioneer's CDJ and XDJ hardware applies Master Tempo as a hardware DSP function. rekordbox software uses the same name. Master Tempo's design priority is real-time stability and low latency in a hardware player context. That's a different engineering goal than Serato's studio-tool lineage. No independent algorithm quality comparison using current rekordbox 7.x exists in published sources. What that means in practice for recorded output at normal offset ranges is not documented with any rigour.

The honest summary: Serato has the strongest documented algorithm heritage and the only comparative test data that favours it at larger offsets. Traktor and rekordbox lack current benchmarks. Serato's advantage is clearest at wide tempo offsets; at the ±3 BPM range of a tightly mixed single-genre set, the differences are less material.

When to Leave It On and When to Disable It

The offset range is the main variable.

  • ±3 BPM or less: Artefacts are minimal on all three platforms. Key lock on, no action needed.
  • ±6% of original BPM or more: Perceptibility increases on transient-heavy material. Serato handles this range better than the documented alternatives. The platform choice starts to matter for the quality of your recording.
  • Wide-range or cross-genre mixing: If you're blending 128 BPM house into 150 BPM techno, key lock is doing significant work. At these offsets, artefacts become part of the character of the recording rather than background noise.

One habit worth building: once you've settled the tempo on a track and you're not planning to move the pitch fader again, disable key lock for that track. You get the pitch correction during the blend, then cut the processing once it's no longer needed. Most software never prompts this. The default-on behaviour never announces itself, and nobody thinks to ask.

A less obvious scenario: key lock running on a track with zero offset applied. If your pitch fader is sitting at centre, key lock is running a processing step that is doing nothing useful. The artefact at zero offset is negligible, but there is no reason to have the algorithm in the chain if you are not offsetting.

What This Means When You're Recording With Ohm

Post-fader USB recording captures what the mixer outputs, downstream of the key lock processing. By the time audio reaches Ohm's input, the decision has already been made. This is true whether your key lock is applied by Serato on a laptop, Traktor, or Master Tempo on a CDJ.

Ohm records the signal it receives. The quality of that signal, including any time-stretch processing, is determined by your setup choices before the audio arrives. That applies to the recording format you choose (covered in Standard, High Quality or Best), and it applies to key lock.

Three things to check before your next recorded set:

  1. Check your typical offset range. Mixing single-genre with pitch fader movement inside ±3 BPM? Key lock on any platform is not meaningfully degrading the recording.
  2. Know which platform's algorithm you're using. Serato's Pitch n Time has documented studio-grade heritage. Traktor and rekordbox have less current comparative data. If you're on either platform and doing wider-range mixing, test with your ears before committing to a promo recording.
  3. Disable key lock on tracks where you've settled the tempo. No offset in use means no reason to be running the algorithm.

For a broader pre-session routine, Five Checks Before Recording Your DJ Set covers the full setup.

Key lock is on by default, it works quietly, and it never announces what it's processing. For casual listening that is fine. For the promo mix going to a label, or the archive set you'll come back to: one conscious decision per session is worth it.