sleexyz/gallium - Githubissues

A web-based environment for live coding music.

http://gallium.live

Setup
Tutorial
Reference
Contributing
Acknowledgements

Setup

You'll need two things:

A browser with WebMIDI support, like Google Chrome, open to gallium.live.
A MIDI output device.

Want to send MIDI to a DAW like Ableton or Garageband? Here are instructions for setting up a virtual MIDI device:

OSX — Set up an IAC bus
Windows — Install loopMIDI
Linux — Enable snd-virmidi

You can also use Gallium directly with a hardware MIDI synth with something like a USB-MIDI cable.

Don't have a DAW or synth? There are great free and open source ones, like TiMidity++ or PureData.

Tutorial

Basics

Use note to start a stream of MIDI notes.

note 60

note can take multiple arguments. The following plays a C-major arpeggio with a cycle of 4 beats:

note 60 64 67 72

You can also write the previous arpeggio with add:

note 60
add 0 4 7 12

What if we want the entire arpeggio to occur all within a beat? We can speed up the stream with fast:

note 60
add 0 4 7 12
fast 4

Transformers can run in parallel with stack. For example, the following plays a C-major chord on every beat:

note 60
stack
  add 0
  add 4
  add 7

Pipes are connected together with do.

Use do in conjunction with stack to do more complex things in parallel. For example:

note 60
stack
  do
    fast 2
    add 12
  do
    fast 3
    add 24

will play a basic polyrhythm of 72's and 84's.

In Gallium, inputs are supplied to operators either with indentation or with spacing.

For example, we can write the previous expression in fewer lines of code by using parentheses:

note 60
stack
  do (fast 2) (add 12)
  do (fast 3) (add 24)

We can even write the whole thing in one line!

do (note 60) (stack (do (fast 2) (add 12)) (do (fast 3) (add 24)))

By default, all expressions in gallium with zero indentation are chained together with an implicit do. In other words,

note 60
fast 2
add 3

with no indentation, really just means:

do
  note 60
  fast 2
  add 3

Multiple Channels

You can send data to up to 16 different MIDI channels with chan. Channels are numbered from 0 to 15.

For example, the following alternates between sending middle C to channel 0 and channel 1:

note 60
chan 0 1

If you want control two channels separately, use it in conjunction with stack. For example:

stack
  do
    note 60
    sub 24
    chan 0
  do
    note 60
    add 0 2 5 7
    chan 1

Advanced: Contextual Numeric Interpretation

In Gallium, numbers are interpreted differently depending on the context.

What does that mean? Let's go through a practical example. Suppose we have a pattern that alternates between two notes:

note 60 80

What if we want to play the 80 twice? We can wrap the 80 in a do and simply add a fast 2:

note 60 (do 80 (fast 2))

This is exactly equivalent to:

alt (note 60) (do (note 80) (fast 2))

where alt is the operator that switches between pipes.

What's going on?

note sets an interpretation for numbers in all its subexpressions. Unless another operator overrides this interpretation (like fast, in our case), all numbers get interpreted with note.

All operators in Gallium that work with numbers behave similarly, including fast and add. See the Reference section for a complete list of operators.

Advanced: Polyphony via Stack-Inversion

We can exploit contextual numeric interpretation to introduce a useful technique called stack-inversion, which allows concise ways to do variations on polyphony.

Here is a stream of C-major triads:

note 60
stack (add 0) (add 4) (add 7)

Writing the add three times can get a bit cumbersome. Stack-inversion allows us to write add just once:

note 60
add (stack 0 4 7)

With stack-inversion, we can whip up a delay effect, which simulataneously plays a stream of notes and then shifted copies of itself:

shift (stack 0 0.5)

where shift is an operator that shifts notes in time by an offset in beats.

Reference

Basic operators

i

i : P

The identity pipe. Takes the input and simply returns it.

m

m : P

The mute pipe. Takes the input and returns nothing.

do

do : ...P -> P

Connects pipes together.

stack

stack : ...P -> P

Runs pipes in parallel.

alt

alt : ...P -> P

Alternates between pipes on every beat.

alt0, alt1, alt2, alt3, alt4, alt5, alt6

alt(n) : ...P -> P

Alternates between pipes every 2^n beats.

Note alt0 is equivalent to alt.

out0, out1, out2, out3, out4, out5, out6

out(n) : ...P -> P

Alternates between pipes every 2^n beats. Pipes perceive time 2^n times slower.

Note out0 is equivalent to alt.

in0, in1, in2, in3, in4, in5, in6

in(n) : ...P -> P

Alternates between pipes every (1/2)^n beats. Pipes perceive time 2^n times faster.

Note in0 is equivalent to alt.

MIDI Operators

note

 note : ...P -> P
(note): Number -> P

Starts a new stream of MIDI notes. note will ignore data from the previous pipe and overwrite it with a new stream.