Rekordbox's key "traffic light" for Serato DJ Pro 4: a small floating panel that shows, for every deck with a track loaded, the key and BPM, the keys that mix with it, and whether the loaded decks fit each other. Keys are drawn in exactly the colours Serato uses in its own Key column.
git clone https://github.com/SM4RTENHEIMER/keylight.git
cd keylight
sh make-app.sh
This builds ~/Applications/keylight.app; drag it to the Dock. To run the bare binary in the
background instead, use ./keylight-start.
macOS 13 or later. Needs nothing but Xcode's command line tools (Swift); no dependencies.
- One row per deck: the deck number, the key as a coloured chip (Camelot, standard notation, or both), the BPM, and the track name.
- Below it the four keys that mix with that track, following Rekordbox's rule: the same key, its two neighbours on the Camelot wheel, and the relative major/minor. The current key is outlined.
- The deck number turns green when the track fits the key of at least one other loaded deck. The green is one Serato never uses for a key, so it cannot be mistaken for one.
The panel floats above every window, also while Serato has focus, and never takes focus
itself. Drag it by its body; its position is remembered. The menu lives in two places, the
♪ icon in the menu bar and a right-click on the panel: show/hide, notation, size
(small/medium/large), "show only while Serato is running" and "start at login". With
the last two enabled the panel appears when Serato starts and disappears when it quits.
"Show matching tracks" in the menu adds one line to the panel, e.g. "23 tracks fit deck 1 · ±6 % · MAIN & POP"; click it to unfold the list itself (up to eight rows, scrollable) and click again to fold it away. The list holds the tracks that fit the deck you are mixing from: compatible key and, by default, within ±6 % BPM. Pick the crate to search in (or the whole library), the BPM window (±3/6/8/12 %, or any), and which deck is the reference: by default the one that has been playing longest, marked with ▸; click a deck row to pin that deck instead (click again to go back to automatic). The list is sorted by kind of match (same key, relative key, neighbours) and then by BPM distance. Clicking a row copies "artist title" to the clipboard so it can be pasted into Serato's search box. Tracks already on a deck are left out.
Serato DJ Pro 4 keeps its library in SQLite
(~/Library/Application Support/Serato/Library/master.sqlite) and writes a row into
history_entry within a second of a track being loaded on a deck; the row's end_time
stays -1 until the deck is cleared or reloaded. The matching list reads asset,
container and container_asset from the same file. keylight opens the database
read-only once a second, and only actually queries it when the database files changed.
It never writes to it. Should a Serato update change the layout, the panel simply shows nothing.
Cost while running: under 1 % of one core, about 15 MB of memory.
The 24 key colours were read off a screenshot of Serato's Key column with
tools/rowsample.swift: A (minor) keys are the bright colours, B (major) keys the dimmer
versions. 12B was outside the screenshot and is derived from 12A. tools/wheelsample.swift
does the same for a Camelot-wheel image and tools/colorsample.swift lists the dominant
colours of any image.
main.swift window, menu, Serato reader
camelot.swift key parsing (Camelot, Open Key, standard notation) and compatibility
camelot_test.swift tests for the key logic: sh test.sh
build.sh compile the binary
make-app.sh compile and wrap as keylight.app with an icon (make-icon.swift)
keylight-start run the bare binary in the background
tools/ colour samplers used to extract Serato's palette
docs/ screenshots for this README and the social preview image
keylight is provided as it is, without warranty of any kind (see the licence). The keys, BPM and matches it shows come from Serato's library and can be wrong or out of date: check them with your ears before you rely on them. The author takes no responsibility for how it is used or for anything that comes of using it, as far as the law allows.
MIT, see LICENSE.
keylight is an independent project and is not affiliated with or endorsed by Serato or AlphaTheta (Rekordbox). It only reads Serato's library file and never modifies it.