Diamond, MIDI Arpeggiator in Ruby

Diamond is a MIDI arpeggiator in Ruby.

It features all of the classic functions of a MIDI arpeggiator plus the ability to live code, algorithmically generate and modify patterns, chain and sync instances and more

This is a quick screencast video I did while live coding Diamond. (read more about this here...)
(Sounds starts around 55 seconds in)

Getting started

Ruby 1.9.2 or JRuby in 1.9 mode are required.

It installs with a typical gem installation...

gem install diamond

Here is a very basic example to get started:

require "diamond"

First, select a MIDI output using unimidi. (more...)

@output = UniMIDI::Output.gets

The Arpeggiator has a number of optional parameters (more...). For the sake of keeping this demo simple, here is a straightforward setup:

opts = { 
  :gate => 90, 
  :range => 4, 
  :interval => 7,
  :midi => @output,
  :pattern => Diamond::Pattern["UpDown"],    
  :rate => 8
}

(read more about what these options mean)

Now create an Arpeggiator object, passing in a tempo value and the options chosen before. In this case the tempo will be 138 BPM

arp = Diamond::Arpeggiator.new(138, opts)

Of course, an Arpeggiator needs notes to work with. As you might expect, it's easy to use a MIDI input for that (see example). However, again for the sake of simplicity here's a chord in Ruby

chord = ["C3", "G3", "Bb3", "A4"]

Use Arpeggiator#add and Arpeggiator#remove to change the notes that the arpeggiator sees. (Arpeggiator#<< is the same as add)

arp.add(chord)
arp.add("C5")
arp << "A4"

By default, the arpeggiator will run in a background thread so if you are working in IRB this will allow you to live code, sync it other arpeggiators, or just run another foreground process. (To start in the foreground, just pass :focus => true to Arpeggiator#start)

arp.start

At that point, the arpeggiator starts playing. All of its options can be controlled on the on the fly.

arp.rate = 16
arp.gate = 20
arp.remove("C5", "A4")

Here are examples showing how to use some of Diamond's other features

• Feeding notes to Diamond using a MIDI controller
• Feeding notes to Diamond using MIDI Message objects
• Live coding Diamond and syncing multiple arpeggiators to each other
• Syncing Diamond to external MIDI clock

Thanks for reading

http://github.com/arirusso/diamond