alda-clj

A Clojure library for live-coding music with Alda.

Background and rationale

See History for a long-winded account of the path that led to alda-clj.

How does it work?

alda-clj is a Clojure DSL that is almost identical to the alda.lisp DSL built into the runtime of Alda 1.x. But instead of being part of the process that generates and plays the Alda score, alda-clj generates a string of Alda code and sends it to the alda client.

The idea is simple: alda is just a low-level tool for playing a score that's already been written (or generated). When you want to go higher-level and create scores programmatically, you can do so in an external process and pipe the result to alda. alda-clj is one way to do this.

Usage

Add the latest version in Clojars to your dependencies:

;; deps.edn
io.djy/alda-clj {:mvn/version "X.X.X"}

;; lein/boot
[io.djy/alda-clj "X.X.X"]

If you haven't already, install Alda and make sure alda is available on your PATH.

alda-clj will shell out and use alda (wherever it's found on your PATH) to play your scores. If desired, you can specify an alternate alda executable by binding alda.core/*alda-executable* to something else, e.g. "/home/dave/Downloads/some-other-alda".

Require alda.core and you're off to the races!

(require '[alda.core :refer :all])

(play!
  (part "piano")
  (for [notes [[:c :e :g] [:c :f :a] [:c :e :g]]]
    (apply chord (map #(note (pitch %)) notes))))

Each time you successfully play! something, the generated Alda code is appended to alda.core/*alda-history*, a string of Alda code representing the score so far that is sent along for context on each call to the alda client. This is what allows scores to be played incrementally, e.g.:

;; conjure a guitar
(play! (part "guitar"))

;; play a few notes on the guitar
(play!
  (note (pitch :e) (note-length 8))
  (note (pitch :f :sharp))
  (note (pitch :g)))

;; play a few notes, still on the guitar
(play!
  (notes (pitch :a))
  (notes (pitch :b) (note-length 2)))

Between invocations of play!, the Alda client "remembers" which instrument(s) were active and all of their properties (octave, volume, panning, etc.) so that the context is not lost.

The history can be cleared at will:

(clear-history!)

You can also stop playback if things get out of hand:

(stop!)

You can conveniently issue arbitrary commands to the Alda client from the comfort of your REPL:

(println (alda "version"))
(println (alda "status"))

Docs, examples

Detailed documentation is available at cljdoc.

There are also example scripts in this repo.

License

Copyright © 2018 Dave Yarwood

Distributed under the Eclipse Public License version 2.0.