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What is JJazzLab?

🎵 JJazzLab is a desktop application which automatically generates backing tracks for any song, even complex ones. It’s a jam buddy to have fun improvising at home, learn new stuff or just practice your instrument. It’s also a great tool for teachers.

🎷 JJazzLab is designed to make non-boring backing tracks, backing tracks with variety, rhythmic accents and dynamics. You can start a solo slowly and gradually build up the atmosphere!

💻 JJazzLab is open-source: platform developers can easily add new features and new music generation capabilities.


Backing tracks

  • Instant generation of a Midi backing track with drums, percussion, bass, piano, guitar, pad, horn section, …

  • Fine tuning of the backing track per song part: rhythm variation, intensity, muted instruments, drum fills, tempo factor, custom phrases, drums transform…

  • Play from anywhere, loop selected bars

  • Play transposed (e.g. for sax or trumpet players)

  • Any song structure: intro, chorus, 1st coda, etc.

  • Adjust tempo, transposition, choose and solo/mute instruments

  • Import user tracks

  • Support for multi-rhythm backing tracks, possibly with different time signatures

  • Export to Midi file, the full backing track or a single instrument track

  • Easy Midi-to-MP3 conversion via export to Midi file

  • Customizable click and pre-count


  • Chord lead sheet editor, song structure editor, chord symbol editor, mix console, song memo editor

  • Multi-file editor with dockable windows

  • Intuitive user interface with unlimited undo/redo, copy/paste between songs

  • Free placement of the chord symbols (quantified or not), off-beat chord symbols anticipation

  • Support all pop-rock and jazz chord symbols, plus user-defined chord symbols

  • Edit chord symbol musical rendering: underlying harmony, accent type, harmony variation during solos, chord symbol substitution, …

  • Drag & drop support to import/export Midi files

  • Customizable song template

  • Customizable UI colors and fonts

  • Print chord lead sheet and song structure


  • Support for Yamaha style files (SFF1 & SFF2 format), access to thousands of free styles on the web

  • Hundreds of embedded rhythms in the installer

  • Support for “YamJJazz Extended Yamaha" style files for even more variations per style

  • Open architecture: new rhythm generation engines can be easily added via plugins

Notes viewer

  • Show backing track notes in real time

  • Show selected chord symbol notes and scales

  • Piano keyboard

  • Guitar diagrams with most common chords, open/close voiced chords, inversions

(pseudo) Arranger keyboard mode

  • Recognize chords played on Midi IN and update the backing track in (pseudo) real-time

Improvisation help

  • Automatic generate improvisation guides on your chord leadsheet

  • Based on Hal Crook's reference book "How to improvise"


  • Connect to any audio engine via Midi: SoundFont player (recommended with the JJazzLab SoundFont), Java internal synth, external synth, VST host via virtual Midi port such as ‘LoopBe1’

  • Compatible with GM/GM2/XG/GS instruments

  • Compatible with any Midi instrument via Cakewalk instrument definition files (.ins)

  • Automatic drums/percussion drum map remapping from Yamaha XG key map to GM/GM2/GS key maps

  • Optimized JJazzLab SoundFont for a high-quality rendering and automatic instrument selection

  • Ready-to-use presets for VirtualMidiSynth (Windows) and FluidSynth (Linux)

  • User-defined default mix per rhythm

  • User-defined default instruments


  • Band-In-A-Box lead sheet files

  • musicXML lead sheet files

  • Impro-Visor lead sheet files


  • Song memo with hyperlinks opened upon song loading

  • Easily add new features thanks to the open-source pluggable architecture

  • Based on the Netbeans application framework

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