Extempore

Extempore is a live-coding environment for music and audio. It pairs a Scheme interpreter with xtlang---a statically-typed lisp that compiles to LLVM IR at runtime---so you can reshape a running program while it keeps making sound. Runs on Linux (x86_64 and aarch64), macOS (Apple Silicon) and Windows (x86_64).

What's new in v0.10.0

v0.10.0 is a consolidation release---nothing changes about what Extempore does, but a lot got faster, safer and tidier under the hood:

• Unified type inference --- the xtlang compiler now drives every compilation through a single constraint-based inference engine. Overload resolution is near-linear (no more compile-time blow-ups on heavily-overloaded call sites) and conflicting constraints report a clearer diagnostic.
• C++20 runtime --- a broad modernisation that retires hand-rolled stand-ins in favour of the standard library and fixes a clutch of latent cross-platform bugs. Building now needs a C++20 compiler (GCC 13+, a recent Clang, or MSVC from Visual Studio 2022).
• Hardened OSC --- the memory-unsafe hand-rolled OSC receive parser is replaced with the bounds-checked oscpp reader, so a malformed or hostile packet is dropped rather than crashing the process.
• --version --- the git tag is now the single source of truth for the version, and a running Extempore can report its own.
• LLVM 22.1.6 --- verified green on all four CI platforms.

Extempore's current stack came together in v0.9.0: LLVM 22 with the ORC JIT (in place of the legacy MCJIT), s7 Scheme (in place of TinyScheme), first-class Linux aarch64, and an interactive --repl (Linux and macOS only). Graphics is now a lean set of WebGPU bindings (via wgpu-native, enabled with -DEXTERNAL_SHLIBS_GRAPHICS=ON); the old OpenGL stack has been retired. If you hit any breakage, please file an issue with a minimal reproducible example where you can.

Getting started

The easy way

Download the latest binary release for your platform, unzip it and run extempore (extempore.exe on Windows) from inside the extempore folder.

Then, set up your text editor of choice and away you go.

Note: the VSCode extension used to offer an Extempore: Download binary command for one-click setup. It hasn't been updated for the current releases and may not work --- downloading the release manually is the safest option for now.

Note on macOS first launch: the binaries aren't signed with an Apple Developer ID, so on first launch macOS will refuse to run them ("apple could not verify ... is free of malware"). Despite the wording, this means Apple hasn't checked the binary, not that anything malicious has been detected --- the release is built in public from the source in this repository by the Release workflow, and you can rebuild it yourself from source if you'd prefer (see below). Signing with a Developer ID requires a paid Apple Developer account, which Extempore (as a research project) doesn't currently maintain.

To clear the quarantine flag on the whole unzipped folder in one go, run:

xattr -dr com.apple.quarantine /path/to/extempore

(replace the path with wherever you unzipped it, e.g. ~/Downloads/extempore). After that, extempore will launch normally.

Build from source

For more information, check out BUILDING.md.

Extempore's CMake build process downloads and builds all the dependencies you need (including LLVM). So, if you've got a C++ compiler, git, CMake >= 3.28 and Ninja, here are some one-liner build commands.

On Linux/macOS:

git clone https://github.com/digego/extempore && cmake -S extempore -B extempore/build -G Ninja -DASSETS=ON && cmake --build extempore/build -j$(nproc)

On Windows (adjust the generator for your VS version):

git clone https://github.com/digego/extempore && cmake -S extempore -B extempore/build -G "Visual Studio 17 2022" -A x64 -DASSETS=ON && cmake --build extempore/build --config Release

Note on build time: the first build takes ~10-30 minutes because LLVM is compiled from source. Subsequent builds reuse the cached LLVM artifacts under build/_deps/.

Note on ASSETS: the ASSETS build-time option (boolean, default OFF) is set to ON above. This will download the Extempore binary assets --- required for many of the examples, but adds a ~250MB download to the build process. If you'd rather not do that, and are happy with some of the examples not working, then set -DASSETS=OFF instead.

Note on running: the extempore binary locates its runtime files (runtime/, libs/, examples/) relative to the source tree at build time. Run it from the build directory (./extempore) rather than installing it to a system location.

Hear your first sine wave

With Extempore running and an editor connected to port 7099, evaluate this and you should hear a 440 Hz tone:

(bind-func dsp:DSP
  (lambda (in time chan data)
    (* 0.5 (sin (* STWOPI 440.0 (/ (i64tof time) SRf))))))
(dsp:set! dsp)

The full example lives at examples/core/hello-sine.xtm.

See Extempore in action

Check out these videos:

• The Concert Programmer
• Interactive, distributed, physics simulation
• Programming in Time
• The Physics Playroom - interactive installation
• An old Graphics Demo
• A Programmer's Guide to Western Music
• Ben's livecoding gig videos

Contributors

The Extempore core team is Andrew Sorensen & Ben Swift. Andrew created Extempore and remains its BDFL; Ben is the current maintainer. For issues and questions the mailing list is the best place to start, but you can also email Ben directly. Many others have contributed to Extempore's development (see the full list) --- including Jim Kuhn, whose significant performance improvements don't show up in the commit logs but for which we're very grateful.

Docs & Community

Extempore documentation can be found at https://extemporelang.github.io/

You can also join the Extempore community:

• Extempore Google group/mailing list
• #extempore on chat.toplap.org (although not as well-monitored as the mailing list)

Cite Extempore

• Extempore: The design, implementation and application of a cyber-physical programming language
• Systems level liveness with extempore

Licence

Copyright (c) 2011-2026, Andrew Sorensen

All rights reserved.

Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met:

1. Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer.

2. Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution.

Neither the name of the authors nor other contributors may be used to endorse or promote products derived from this software without specific prior written permission.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.