SlapAsSound has released GroovEmu Arranger, a free Windows system that turns REAPER into a live arranger-style workstation.
This one comes from Marko Karja, a developer from Estonia who has sent BPB some unusual free plugin experiments over the years. His product pages usually have a strong sense of humor, but under the playful presentation here is a real tool that could be useful if you like building arrangements in REAPER and then playing them more like an instrument.
The basic idea behind this one is similar to that of a hardware arranger keyboard. You prepare an arrangement, play chords with your left hand, and GroovEmu follows those chords live while handling variations, fills, intros, endings, and other arranger-style performance elements.
GroovEmu is built specifically for REAPER, so this is not a general-purpose plugin for every DAW. REAPER works as the host in the background, but the developer says you do not need to be an experienced REAPER user to start playing with the included demo project.
The system is built around two main parts. GroovEmu Reaper Engine handles the REAPER-side arranger workflow, while GroovEmu Live Transposer handles live chord control and accompaniment transposition.
In Edit Mode, you build the arrangement on the REAPER timeline using variation and fill regions, rhythm parts, accompaniment parts, instruments, and effects. In Live Mode, the PLAYER region performs the active variation or fill while your left-hand chords guide the harmony.
You can also set a split point for accompaniment and solo playing, adjust tempo and play rate, set the global song key, trigger fills and variations, and use your right hand for solo parts.
GroovEmu also includes GroovEmu Sound Module, a shared sound module with 128 essential instruments. These aren’t mind-blowing, but they give the user the same basic sound source for demo projects and shared styles, though you can replace them with your own VST instruments and libraries (our free Kontakt libraries page is a good place to start).
The installer includes the GroovEmu Reaper Engine, GroovEmu Live Transposer, GroovEmu Sound Module, a ready-to-play demo project, and user manuals. There is also a Health system that can rebuild important tracks, plugin routing, names, settings, and VAR/FILL setup if something breaks while you are experimenting.
I can see this being interesting for keyboard players accustomed to working with arranger keyboards. But it can also work for REAPER users who want to test new workflows and anyone who wants to test chord progressions and arrangement ideas without constantly stopping playback and editing MIDI by hand.
GroovEmu Arranger is available for Windows and requires REAPER. The download is free, with no subscription, account, or hidden fee required.
Download: GroovEmu Arranger (FREE)
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Last Updated on August 11, 2026 by Tomislav Zlatic.
