in which lisp generates musicLivecoding Music with Fennel and Renoise		Author	abhirag
		License	AGPL
Version	3.5.4	Source	GitHub

Livecoding Music with Fennel and Renoise

tl;dr

I extended the Rust library powering algorithmic music generation capabilities in Renoise digital audio workstation to also support Fennel
So now you can write Fennel (a Lisp that compiles to Lua) and create music:

Dynamically load the custom shared library, restart Renoise, jump to the built-in script editor and begin your script with --! fennel pragma, like so:

--! fennel
(pattern {:unit "1/4"
          :pulse [1 0]
          :event ["c4"]})

Optionally install the companion tool I created for live-reloading .fnl and .lua files if you don’t want to be tied to the Renoise script editor and want to use your own code editor. Also grab the fennel-ls docset for editor support
Enough ceremony, go make some noise!

Why?

It’s hard to argue against programming being an art form when programs can sound like this:

Programming and creating music are the two things that have always helped me drown out the noise around me (and in my head). It has been a few years, but I still clearly remember the day I found Overtone and Emacs Live, I was instantly hooked and Sam Aaron’s work has inspired me ever since. I realized live coding is about expressing myself and found Lisp to be perfect for that. A language willing to bend at my every whim. Malleable. Mine.

So when I found that:

Renoise was now shipping with support for programmatically creating music in Rust or Lua
The dynamically loaded library behind it was open source and written in Rust

…it was enough for me to be nerd sniped into adding support for Fennel. I would be remiss not to mention Ramsey Nasser’s 8FL which is also a direct inspiration.

How?

The library already embeds a Lua VM via mlua for evaluating user scripts, which we’ll refer to as the engine VM hereon
To effectively sandbox user scripts, the engine VM is not given the LuaStdLib::PACKAGE capability which allows loading external Lua modules
The Fennel compiler is itself a Lua program that requires this capability to bootstrap its submodules, so a second dedicated compiler VM (the Fennel VM hereon) is spawned with it
The Fennel compiler source is vendored and compiled to bytecode once per process and reused across VM instantiations; when the Fennel VM is created, this bytecode is loaded and executed in it, producing the fennel module with a compileString function
Fennel scripts are passed to compileString, which returns Lua source that is then handed off to the engine VM for evaluation
A prelude compiled into the shared compiler scope provides custom macros to all scripts without explicit imports; src/bindings/prelude.fnl is where more macros can be added

Renoise with Fennel pattrns — Renoise with a Fennel phrase script in the built-in editor

What Else?

Also created a companion Renoise tool that watches a directory for .fnl and .lua files and live-reloads them into Renoise phrase scripts, so you’re not tied to the built-in script editor. Files follow a [instrument_index]-[phrase_index].(fnl|lua) naming convention to map to the right instrument and phrase
Also added a fennel-ls docset for the pattrns API, providing autocompletion and inline documentation when editing Fennel scripts in your own editor

Fin?

This is just the beginning, on to the fun part, making music!
Thanks to the Renoise devs for open sourcing pattrns! I’ll reach out soon to see if there’s room for Fennel support upstream
Also thanks to bakpakin, technomancy and the rest of the Fennel contributors for building such a great language
If this kind of thing appeals to you, which is frankly a niche within a niche, we probably have a lot in common. Let’s talk, potential friend!