What is Spektra?

• Position: BPM across, Energy up. Tracks without a BPM from your DJ software sit in the NO BPM gutter on the far left.
• Size: Bass Density. Heavier low end reads larger.
• Brightness: Color, a track’s tonal character, from dark and muted to bright and airy.

All of it is measured from the audio; nothing on the map is typed by hand. Clusters, outliers and gaps show up at a glance. Click a star to audition it, drop up to five anchors, and plot a course between them.

It exports playlists because that’s the fastest way to get a discovery into the DJ software you already use. Some people plot a course and play it top to bottom; others pull two tracks out of it and move on. Both are fine.

The point is what you find on the way there.

No account, no cloud, no subscription, no telemetry. Analysis, including the audio model, runs offline on your own computer. Bought once and owned, the way software used to be.

The model turns each track into an embedding, which powers Similar Sounding, Sound Like and part of Energy. The rest is measurement: spectral analysis of loudness, low end and tone.

When you plot a course, Spektra sequences tracks you already own, using the anchors, track count and Trajectory you chose. Nothing on the map is invented.

Spektra listens to a few slices of each track to compute an embedding.

Embeddings drive:

• Sound Like: your anchors rank the rest of the library by closeness, and the map tints every star by its nearest anchor.
• Courses: how smoothly one track sounds into the next.
• Energy: the model’s reading of intensity is part of the score.

“Sounds alike” to the model is a useful approximation, not a promise that two tracks mix well. Embeddings also don’t decide where a star sits on the map; see why similar tracks can be far apart.

What goes in. Spectral analysis measures impact (Power), how busy the percussion is, and low-end weight (Bass Density). The audio model adds its own sense of intensity, so a sparse track with a pounding kick can outrank one that just sounds busy.

Where it falls short.

• It’s relative to your library. Scores are scaled to your own collection: 50 is the middle of your library, not of all music. Importing a lot of new tracks can shift existing scores.
• Mastering counts. Heavy compression and limiting push a score up. A dynamic, quieter master can score lower than it feels.
• Context isn’t in the number. Perceived energy is subjective and depends on what played before: a 60 lifts the room after a run of 40s and lets it breathe after a peak. Spektra scores each track on its own.
• One number per track. A track that builds slowly gets a single score, weighted toward its most intense section.

Until every track has its embedding, Energy uses the spectral half alone and Spektra marks it as provisional. The recipe may change as it gets tuned.

• Power: impact and weight. Dense, heavily compressed tracks score high.
• Bass Density: dominant sub-bass and thick basslines score high; airy, treble-led tracks score low. It sets a star’s size on the map.
• Color: dark tracks are industrial and dub-heavy; bright tracks are airy, with extended treble. It sets how bright a star is.

Because the scores are calibrated to your library, a 70 means “high for your collection”. Power and Bass Density also feed Energy.

Get the installer for your system from the download page. macOS builds are signed and notarized. The Windows installer isn’t code-signed yet, so Windows shows a warning the first time; see why Windows warns me.

On Linux, the deb is for Ubuntu, Debian and distros built on them, such as Linux Mint and Pop!_OS. On anything else, including Fedora, use the AppImage. Older releases such as Ubuntu 20.04 or Debian 11 can’t run Spektra: the deb won’t install, and the AppImage can’t open your library.

1. Run the installer. SmartScreen shows Windows protected your PC.
2. Click More info.
3. Click Run anyway. The installer carries on as normal.

v1.0 will be signed. macOS builds are signed and notarized and install without a warning.

• Mixxx: Spektra reads its library directly. See importing from Mixxx.
• Rekordbox: Spektra reads a collection you export as XML. Streaming tracks have no local file, so there’s nothing to analyse. See importing from Rekordbox.

BPM and key come from your DJ software. M3U8 is a plain playlist format that Mixxx and plenty of other DJ software import. Spektra can’t import Serato, Traktor or Engine DJ libraries.

Spektra keeps its analysis in its own database. The only files it writes are the ones you ask for: M3U8 exports and, for Rekordbox libraries, Spektra’s own Link File, which Rekordbox reads only when you import a playlist from it.

Close Mixxx before you import or sync, because Spektra can’t read Mixxx’s library while Mixxx has it open.

1. In Rekordbox: File → Export Collection in xml format.
2. In Spektra, choose the Rekordbox card when you connect your library, then choose that file.

Export the whole collection, not a single playlist. Streaming tracks (Beatport, Tidal, SoundCloud and the like) have no local audio file, so Spektra skips them and counts them in Sync history.

Your Rekordbox playlists show up as Rekordbox Playlists, which you can use as filters. BPM and key come from Rekordbox. To pick up changes later, see updating your library.

Rekordbox import arrived in Spektra 0.10. On an older version, update first.

Spektra can’t read Mixxx’s library while Mixxx has it open, so close Mixxx first. If Spektra doesn’t find it, choose the mixxxdb.sqlite file yourself:

• macOS: ~/Library/Containers/org.mixxx.mixxx/Data/Library/Application Support/Mixxx/
• Windows: C:\Users\<you>\AppData\Local\Mixxx\
• Linux: ~/.mixxx/

Your crates show up as Mixxx Crates, which you can use as filters. BPM and key come from Mixxx.

• Rekordbox: export your collection again to the same file first. Spektra reads that export, not Rekordbox itself.
• Mixxx: close Mixxx, then sync.

When the source file is newer than your last sync, the status bar says Library Needs Sync. Turn on Auto-sync on startup to sync every time Spektra opens.

If you moved the library file, use Locate file… instead. It keeps your tracks, their analysis and your saved Playlists.

Start from Settings → Library Management → Replace library…. Every track in the new library is analysed from scratch, which takes a while for a large library. Your Short tracks setting carries over.

Moving the same library to a new place is different: use Locate file…, which keeps everything.

The files need to be on a drive your computer can reach when Spektra analyses them. If a file can’t be read, it’s listed under Show Issues in Library Management with the reason, and you can clear the record to try again.

Analysis runs in two passes: spectral analysis, then the audio model.

• The Observatory opens as soon as the first tracks are ready. Filtering, inspecting and auditioning work throughout.
• Plot Course becomes available once every track has its embedding. Until then, Energy is marked provisional.
• Stars can shift a little as analysis finishes, because scores are calibrated to the whole library.

You can Pause Analysis and resume it from Library Management. For a long first run, turn on Prevent Sleep in System Settings.

A track without a BPM is still analysed. It sits in the NO BPM gutter on the left edge of the map, because it can’t be placed by tempo.

Key Notation in App Settings shows keys as stored (Original), in Open Key, or in Traditional notation. If a key or BPM is wrong, fix it in your DJ software and sync.

• Still analysing: stars appear as tracks finish.
• Short tracks: with Exclude short tracks on (Settings → Library Management), tracks under your minimum length stay off the map and out of Courses. You can still add one to a Playlist by hand.
• Couldn’t be read: Show Issues in Library Management lists each file and why.
• No local file: Sync history counts files not found and streaming tracks.
• Filtered out: an active filter narrows what’s shown.

Tracks without a BPM aren’t missing: look in the NO BPM gutter on the far left.

To find tracks that sound alike, click a star and look at Similar Sounding, or make it a Sound Like anchor: the map tints every star by its nearest anchor, so its sonic neighbours light up wherever they sit.

Size and brightness (Bass Density and Color) give a rough sense of sound at a glance.

• Path: walks from anchor to anchor in the order you added them. Order matters.
• Either: alternates tracks near any anchor.
• Blend: tracks that sit between all the anchors.

Then set a track count and a Trajectory, and click Plot Course.

The map tints every track by its nearest anchor, but a Course draws only from each anchor’s closest matches; distant tracks stay on the map for context. Anchors join the pool but aren’t guaranteed a place in the Course.

Click Save Playlist to keep a Course. Playlists are listed in the sidebar, where you can open them, add tracks by hand and export them.

You can export a Course as an M3U8 file without saving it. The Rekordbox Link File carries saved Playlists only.

In Mixxx, right-click Playlists in the library sidebar and choose Import Playlist.

• Naming Pattern in App Settings sets the exported file’s name.
• Export all playlists in App Settings backs up every Playlist at once.
• The file points at your audio files by their paths, so it works on the computer that has them.

Rekordbox can import M3U8 too, but the Link File is easier and keeps tracks M3U8 import would skip.

You’ll find it under Link File in Settings → Library Management.

Once:

1. In Rekordbox: Preferences → View → Layout, tick rekordbox xml.
2. Preferences → Advanced → Database → rekordbox xml → Imported Library: choose the Link File.

Each time you want a playlist in Rekordbox:

1. In the rekordbox xml tree, click ↻ to load the latest playlists.
2. Right-click a playlist under Spektra → Import Playlist.
3. If Rekordbox asks whether to load tag information, choose No.

Changes you make in Spektra after importing a playlist don’t reach the copy in Rekordbox: import it again and let Rekordbox overwrite its copy. Deleting a playlist in Spektra doesn’t remove it from Rekordbox. A Course has to be saved as a Playlist before it appears.

The warning says how many tracks Rekordbox will skip and names them. To get them into Rekordbox, import through the Link File instead, which writes paths exactly as Rekordbox stores them.

Mixxx isn’t affected.

Feedback is anonymous: no name, email or device identifier is sent. Every Feedback gets read, but there’s no way to reply to it, so email [email protected] if you want an answer.

For bugs, tick Include recent log. You see exactly what will be sent before it goes. What the app sends lists every field and how long it’s kept.