Looper

An arranged live looper for macOS. Script your loops on a timeline, press Record, and perform hands-free.

Most loopers make you stomp a pedal at exactly the right moment, for every layer, every time. Looper turns that around: you draw the song first, then you just play it.

• A record region (red) says "capture what I play here".
• A play region (green) says "loop that recording here".

Press Record and the playhead walks the timeline. You hear yourself inside the record regions, and everything you played comes back exactly where you scripted it. Your hands stay on the instrument.

What it does

• Slice playback. A play region can loop any part of a recording, in any subdivision. Record four bars once, then loop bars 1 to 2 in the verse, bars 3 to 4 in the chorus, and a single 16th note as a stutter fill.
• Audio and MIDI. Audio tracks loop your input. Instrument tracks loop the notes and replay them through a plugin.
• Recorded dry, played through the effects. Change a track's plugins and every loop on it follows.
• Plugin host. VST3 and Audio Unit instruments and effects, one chain per track.
• Any output. Every track picks its own input and output pair, including the click track and talkback, so the band hears the click and the audience does not.
• Takes, reference takes and Panic. The last 8 takes of every recording are kept. Mark a good one as the reference, and one pedal press swaps it in when you fluff a part live.
• Automation tracks. Command tracks put transport, mutes and effect switches on a pedal, or fire them by themselves at a bar. Control tracks draw curves or route a fader to any plugin parameter.
• Play it from the laptop. With no MIDI keyboard connected, the computer keyboard plays the selected instrument, and drum tracks get a full kit on the keys.
• The recording follows the script. While recording, whichever instrument has a record region coming up becomes the live one. No mouse.

Status

v0.1 is an early build. It was written in one long session and has been used for hours, not months.

Checked so far: the loop engine (a self-check proves slices play back sample-exact), drawing and moving regions, MIDI recording and looping through Apple's built-in synth, saving and loading songs.

Not yet proven on a stage: audio input with a real instrument and interface, latency compensation by ear, third-party plugins, hardware pedals and faders. Expect rough edges and please report them.

Apple Silicon only for now.

Install

1. Download Looper-0.1.0-macOS-arm64.zip from Releases and move Looper.app to Applications.
2. The app is not notarized, so macOS blocks the first launch. Run this once:

xattr -dr com.apple.quarantine /Applications/Looper.app

3. Allow the microphone when asked. Without it, audio tracks record silence.

Quick start

1. Right-click a track and choose "Record region here". Drag its right edge to make it four bars.
2. Right-click after it and choose "Play region here". Stretch it as long as you like.
3. Press Return to record and play your part. It loops by itself.
4. Select the play region. The strip at the bottom shows the recording with a green window on it. Drag the window to choose which slice loops.

Key	Action
Space	Play or stop
Return	Record or stop
R or ,	Back to the beginning
.	Jump to the next marker
Q	Loop the selected region (when the loop range is switched on in Prefs)
L	Lock the track (rehearse without overwriting)
P	Panic
Z, Shift-Z	Undo, redo
Backspace	Delete the selection

Drag on empty space to select several regions, drag a selection to move it, Alt-drag to copy it. Double-click a recording to name it.

Markers: add a marker track from "+ Track", right-click it to drop a named marker, and press . to jump from one to the next.

Track names: edit the name at the top of the right panel, or right-click the track's name.

Instrument tracks: A S D F G H J K play one octave from middle C, with W E T Y U for the black keys.

Drum tracks:

Key	Drum	Key	Drum
`	Crash left	Q	Closed hat
1	Crash right	W	Pedal hat
2	Ride	E	Open hat
3	China	A	High tom
Z	Kick	S	Mid tom
X	Snare	D	Low tom

Songs are folders named Something.looper in ~/Music/Looper/ and they autosave.

Tell it what to build

The running app takes commands from outside, so an AI coding assistant can turn a sentence into an arrangement:

"Start with a 2 bar kick and snare recording, then layer hi-hats on it, then add bass, and when all three are layered let them run for 4 bars together."

Open this repo in Claude Code with Looper running and say it. The tracks and regions appear on the timeline. The command format is small and documented in docs/CONTROL.md, so any script can use it too.

Build from source

You need the Xcode Command Line Tools, CMake and Ninja. Full Xcode is not required.

xcode-select --install
brew install cmake ninja
git clone https://github.com/LevNyyon/looper.git && cd looper
git clone --depth 1 --branch 8.0.15 https://github.com/juce-framework/JUCE.git third_party/JUCE
cmake -S . -B build -G Ninja -DCMAKE_BUILD_TYPE=Release
cmake --build build --target Looper selfcheck
build/selfcheck
open build/Looper_artefacts/Release/Looper.app

How it is built

C++17 and JUCE 8, nothing else.

Folder	What is in it
engine/	The looper core: a script of record and play regions driving loop buffers. Standard library only, no devices, no UI. selfcheck.cpp is its one check.
app/	The JUCE app: song model and file format, audio and MIDI host, plugin chains, timeline UI, automation.
docs/CONTROL.md	How to drive the running app from outside: the command inbox and its ops.
PLAN.md	The working plan: scope, decisions, every deliberate shortcut and what was and was not verified.

The core is small because everything is known in advance. A record region has a fixed length, so its buffer exists before you play a note, and a play region is just a read position: sliceStart + ((playhead - regionStart) mod sliceLength).

Shortcuts that were taken on purpose are marked in the code with a ponytail: comment naming the limit and the upgrade path.

Credits

Looper is inspired by ALK2 by zenAud.io, a wonderful arranged looper that was discontinued in 2021. This is an independent reimplementation of the idea, written from scratch from the public manual. It contains no ALK2 code and is not affiliated with zenAud.io.

License

GNU AGPL v3, the license JUCE is free under.