project name: repl-looper
project url:
author: awwaiid
description: mash of REPL and looper; a live performance code sequencer with web UI
discussion url:
tags: sequencer looper grid


Anagogically integrated UI for Norns / Matron / Grid

Experimental performance and creative tool, mashing together several things that I like. REPL (Read-Eval-Print-Loop, a code execution console) for interactive code creating. Grid to have a tactile UI (maybe we’ll throw in a midi pedal too). Dance between sound-generating code, recording commands, looping, slicing, mixing, generating tools and patterns on the fly, and maybe make some self-modifying loops.

Check out the dev branch and dev branch development journal for ongoing development work. The main branch is the current “stable” (haha) version.

Recent Releases


Install directly from maiden or by running this in the maiden/matron console:


Then start repl-looper on the norns.

There are two ways to interact with repl-looper – Directly on the norns with a USB keyboard, or with a web browser. Both ways work with a monome-grid (optional).

You can access the web interface at: or http://norns.local/api/v1/dust/code/repl-looper/ui/dist/repl-looper.html

Both interfaces offer the same REPL functionality, but the web-UI adds some further visualization.

Basic Usage

The workflow is an alternative to maiden’s REPL with a few different features and style. The basic idea is the same – you run Lua commands and see the results. Verify that everything is running with some simple math, type in:


Which should output 4 (give or take). While you can run any Lua commands you want, repl-looper comes with a built-in engine and a bunch of tools. The built-in engine is a mash-up of Timber, Goldeneye, and Molly the Poly, along with some lua wrappers. Try these commands:

-- Timber piano shortcut


Press <tab> for some completions. You can press <up> or <down> arrows to select previous commands or tab-completion choices. Press <enter> without any command to run the previous command again.

Next thing to play with is loops/sequences. There are 8 pre-defined 16-step loops, one for each row, put into variables a to h. Start by recording into loop a:


Loop a is now playing and recording! You can see the current step and steps with recorded events on the grid. Now run:


Wait a bit, and then run:


The loop is playing and will wrap back around at 16 steps and keep recording, so if you add more events they stack up on top of each other. Now try:

a:stop() -- this stops recording but keeps playing
a:stop() -- stop again to also stop playing

At this point press some of the grid buttons to trigger all the events recorded at that step immediately (this ignores their sub-step timing). Here are a few more things to try:

a:show() -- show the loop contents
a:play() -- start loop again
a:clear() -- erase loop contents

Now that you have the script running on norns and the local UI up in a browser and everything working together, read through the Usage Reference below and Techniques to get more some ideas!


Fullish Usage Reference


Library and Live-Coding Helpers

There are a lot of pre-defined variables, functions, and objects to make live-coding with repl-looper convenient. These have been built organically based on usage, suggestions are welcome! In particular tab-complete-friendly prefixes for method names could be improved.

Pre-defined variables/functions


There are 8 pre-defined loops, a, b, c, d, e, f, g, and h. Each loops is assigned to a row on the grid. So a is on the first row and h is on the bottom row.

Here we use loop a as the example, but you could run these commands on any loop.

Engine wrappers

BONUS: all object wrapper


When developing you can run the Web-UI directly on your laptop, but you’ll need to use docker or install dependencies (nodejs/npm). You get live-reload of changes and such. Slightly-evil the dist dir is then checked in to git for serving from the norns/maiden webserver. For the UI (a VueJS app):

cd ui

# Direct
npm install
npm run dev

# OR Docker, if you like
docker-compose up

On the norns side we need to run the lua server-side. During dev I do it this way:

# Auto-push to norns

Future Ideas

Shout Outs!