IoniandorianphrygianLydianMixolydianaeolian ↻

APU Harmonic DJ helps you find tracks that work well together and arrange them into a DJ set. It analyzes the key, mode, and BPM of your music, with separate key analysis for the first and second halves of each track.

Generate a tracklist, listen to the suggested tracks, and keep refining it. Harmonic compatibility narrows the search, but rhythm, phrasing, and energy still need your ears.

01

Analyze locally

Search your Library by key, BPM, and track information. Rate your favorites and compare loudness. All audio analysis runs on your computer.

02

Plan complete Mixes

Choose a track count and generate a Mix. Lock tracks in place, exclude ones you don't want, and generate the rest again.

03

Find the next track

Use Gem Finder to search for a particular key relationship, listen to the matches, and choose what comes next.

04

Save your favorites

Save and rate track pairings as Gems so you can find them again when planning another Mix.

The five-track limit applies only to the free Community edition. Pro supports larger Mixes, Gem Finder, and saved Gems. Both editions use the same analyzer.

From Library to Mix

Start with a folder of tracks in a similar tempo range. Once they’re analyzed, choose your track count and generate a Mix. Listen to the result, then adjust the settings or try different tracks.

1

Build a Library

Add files or folders, then browse and listen to analyzed tracks while the remaining files are processed.

2

Generate a Mix

Start with the defaults, or choose your track count, BPM settings, Library groups, allowed keys, and transition profile.

3

Refine by ear

Lock tracks you want to keep, try alternatives, and regenerate the remaining positions.

4

Save a Mix

Every Mix is named and auto-saved. Keep editing, duplicate a variation, and return to the undo history later.

Harmonic DJ Library showing synthetic tracks with detected keys and BPM — Search, filter, group, rate, and audition analyzed tracks without waiting for the rest of the Library to finish.

Rate local or shared tracks from one to five stars. When several tracks fit similarly well, higher-rated tracks are more likely to be chosen. Ratings don’t override your key, BPM, exclusion, transition, or Gem rules. You can also switch key profiles without analyzing the audio again.

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Plan a Mix

Harmonic DJ evaluates the whole tracklist. It compares the weakest transition first, then the next weakest, so a few strong pairings don’t hide a poor one. Your track ratings help choose between otherwise similar options.

Six-track Harmonic DJ Mix with locks, roles, key changes, BPM, and gain guidance — Lock tracks you want to keep and regenerate the open positions. Each Mix stores its tracklist and generation settings together.

Exact track counts

Choose how many tracks you want. If no complete tracklist satisfies your settings, the current Mix stays unchanged.

Incoming and outgoing keys

By default, transitions compare the second half of one track with the first half of the next.

BPM options

Match tracks by rounded BPM, allow deck-style speed and pitch changes, or keep each track at its original tempo.

Gain guidance

Per-track gain recommendations help match playback levels. A shared Mix gain adjusts the level before limiting.

Harmonic DJ is a planning and listening tool. Beatmatching, phrase alignment, cue points, and performing the transitions are still up to you.

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Gem Finder

Gem Finder lets you search for the next track from a particular position in your Mix.

Choose the incoming parent key and mode you want to try, then listen to matching tracks. You can play a sustained piano chord to hear the target harmony, or broaden the search if there aren’t enough matches. Add the track you like to the Mix and save the pairing as a Gem.

A Gem records a transition you've listened to and want to use again.

Harmonic DJ Saved Gems showing synthetic directed transitions and personal rankings — Each Gem has a direction: track A into track B. The reverse transition is a separate pairing.

Pro includes Gem Finder and lets you save, rate, and reuse Gems. Browse saved pairings by source track, add them to another Mix, or drag their local audio files into another application. Community can still open and play your existing Pro Mixes and Gems.

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Keys and Modes

Harmonic DJ detects six modes: Ionian, dorian, phrygian, Lydian, Mixolydian, and aeolian. It can compare tracks by their tonic or by their shared parent scale, and it accounts for key changes between the first and second halves of a track.

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Transition profiles choose which key relationships a Mix allows. Start with General Purpose, or use a narrower profile to try a particular type of transition.

Modal detection

Key analysis includes modes such as dorian and Mixolydian alongside the familiar Major and minor scales.

Track halves or whole tracks

Use separate incoming and outgoing keys, or combine both halves into a whole-track key estimate.

Transition profiles

Choose a factory profile or save your own set of allowed key relationships.

Analysis contours

Compare calibrated-flat, ECMA-418, and the two ISO 226 profiles without rescanning your Library.

These settings are optional. You can generate your first Mix with the defaults and explore the key relationships as you listen.

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Local Audio Stays Local

Your audio and Library stay on your computer. Analysis and playback run locally, and Harmonic DJ does not upload your tracks for analysis or license checks.

Harmonic DJ Share Mix page with synthetic editable tracklist details — Edit the tracklist's display names, copy it as text, or publish a Mix page you can share with a link.

Community and Pro can copy or publish any editable saved Mix.

Published Mix pages show the tracklist, keys, BPM, and transition strategy. They don’t include your audio, file paths, raw analysis, or editing history. To publish your first Mix, follow the review link sent by email and confirm Publish and view Mix. Later changes stay local until you choose Update Mix. The link stays the same, and you can unpublish the page when you no longer want to share it.

You can also share a collection file with another Harmonic DJ user. It contains track information, groups, BPM, key analysis, and loudness measurements, but no audio, file paths, or personal ratings. Library metadata export is available separately for your own backups and includes paths and ratings.

Mix files and transition presets don’t contain audio either. Tracks from a shared collection become playable when you add your own copies to the Library.

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Community and Pro

Community is free and doesn't require an account. It includes named, auto-saved Mixes of up to five tracks. Pro removes that limit and adds Gem Finder and saved Gems. Both editions use the same application and Library.

Free forever

Community

Analyze your music and build as many saved Mixes as you want, with up to five tracks in each.

Unlimited local analysis and audition
Library search, filters, groups, personal ratings, and maintenance
Share collections with other Harmonic DJ users
All key profiles and Mix Settings
Named, auto-saved Mix documents with one to five tracks
Create, rename, duplicate, import, export, undo, and refine Mixes
Copy or publish saved Mixes
Import and export Mix files, and manage transition presets
Open and audition existing Pro Mixes and Gems, and drag their playable tracks to other applications

Sale price · $30.00 one-time · Regular price $40.00

Pro

Everything in Community, without the five-track limit, plus tools for finding and saving Gems.

Create and edit Mixes longer than five tracks
Choose larger exact track counts
Gem Finder and Find Next Gem
Save, rate, browse, and reuse Gems

Try Pro without a payment card. If the trial ends or a license becomes inactive, Harmonic DJ returns to Community while the Library, Mixes, Gems, collections, and presets remain stored.

Download Community

Formats: standalone application and VST3 on macOS (Intel and Apple silicon), Windows (x86 and x64), and Linux (x64); Audio Unit on macOS; and AAX on macOS and Windows. Keep the standalone application installed when using the plug-ins; they share its Library. Windows N and KN editions require the Microsoft Media Feature Pack.

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Credits

Developed by APU Software, LLC with the following libraries:

JUCE (cross-platform audio and user interface framework)
Boost (header-only algorithms)
r8brain (sample rate conversion)
PFFFT (FFT library)
TagLib (audio metadata)
utf8cpp (Unicode support used by TagLib)

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