What is JJazzLab?

JJazzLab is a Midi-based application which automatically generates backing tracks (a musical accompaniment) for any song. It’s a jam buddy to have fun improvising, learn new stuff or just practice your instrument. It’s also a great tool for teachers.

JJazzLab screen capture



  • 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, …
  • Play from start, from selected bar, or loop selected bars
  • Any song structure: intro, chorus, 1st coda, etc.
  • Adjust tempo, transposition, choose and solo/mute instruments
  • Support for multi-rhythm backing tracks, possibly with different time signatures
  • Export to Midi file, enabling easy Midi-to-MP3 conversion
  • Customizable click and precount


  • Chord leadsheet 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, off-beat chord symbols anticipation
  • Support all pop-rock and jazz chord symbols, plus user-defined chord symbols
  • Edit chord symbol rendering: underlying harmony, accent type, harmony variation during solos, …
  • Force section to start on a new line
  • Customizable song template
  • Customizable UI colors and fonts


  • 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


  • 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 key 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 files
  • musicXML files
  • Impro-Visor files


  • Autoupdate notifications
  • Based on the open-source Netbeans application framework