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Beats Drum Machine

Beats is a command-line drum machine written in pure Ruby. Feed it a song notated in YAML, and it will produce a precision-milled *.wav file of impeccable timing and feel. Here's an example song:

  Tempo: 105
    - Verse:  x4
    - Chorus: x4
    - bass:     house_2_1.wav
    - snare:    roland_tr_909_2.wav
    - hihat:    house_2_5.wav
    - cowbell:  big_beat_5.wav
    - deep:     house_2_2.wav

  - bass:     X..X...X..X.....
  - snare:    ....X.......X...
  - hihat:    ..X...X...X...X.

  - bass:     X..X...X..X.....
  - snare:    ....X.......X...
  - hihat:    XXXXXXXXXXXXX...
  - cowbell:  ....XX.X..X.X...
  - deep:     .............X..

And here's what it sounds like after getting the Beats treatment. What a glorious groove!

For more, check out


To install the latest stable version (2.1.0) from, run the following from the command line:

gem install beats

Note: if you're installing using the default version of Ruby that comes with macOS, you might get a file permission error. If that happens, use sudo gem install beats instead. If you're using a version manager such as rbenv, chruby, or RVM, plain gem install beats should work fine.

Once installed, you can then run Beats from the command-line using the beats command.

Beats is not very useful unless you have some sounds to use with it. You can download some example sounds from


Beats runs from the command-line. Run beats -h to see the available options. For more detailed instructions, visit on the Beats Wiki.

Check out this tutorial at to see an example of how to create a beat from sratch.

What's New in v2.1

The latest version of Beats is 2.1.0, released on September 9, 2017.

This version adds support for composite sounds. That is, sounds that are made by combining two or more sounds together. They are a more succinct way of writing songs where multiple tracks play the same rhythm.

Composite sounds can be defined in the Kit by putting multiple sound files in an array:

  - bass:         bass.wav                    # A traditional non-composite sound
  - combo_snare:  [clap.wav, 808_snare.wav]   # A composite sound

The combo_snare sound above is a composite sound made by combining clap.wav and 808_snare.wav together. It can then be used in a pattern:

  - bass:         X.......X.......
  - combo_snare:  ....X.......X...

This is equivalent to the following song:

  - bass:   bass.wav
  - clap:   clap.wav
  - snare:  808_snare.wav

  - bass:   X.......X.......
  - clap:   ....X.......X...
  - snare:  ....X.......X...

When using the -s command-line option to write each track to its own *.wav file, each sub-sound in a composite sound will be written to its own file. For example, this song:

  - combo_snare:  [clap.wav, 808_snare.wav]

  - combo_snare:  X...X...X...X...

...will be written to two different files, combo_snare-clap.wav and combo_snare-808_snare.wav, when using the -s option.

Finally, when defining a track in a pattern, multiple sounds can be given in an array as a composite sound. Kit sounds and non-Kit sounds can be used together:

  - bass:         bass.wav
  - combo_snare:  [clap.wav, 808_snare.wav]

  - [bass, combo_snare, other_sound.wav]:   X...X...X...X...

This is a equivalent to:

  - bass:   bass.wav
  - clap:   clap.wav
  - snare:  808_snare.wav

  - bass:             X...X...X...X...
  - clap:             X...X...X...X...
  - snare:            X...X...X...X...
  - other_sound.wav:  X...X...X...X...

What's New in v2.0

The previous version of Beats is 2.0.0, released on September 4, 2017. It is primarily a modernization release, and contains some relatively small backwards incompatible changes.

  • Track rhythms can now have spaces in them. For example, X... .... X... .... is now a valid rhythm. Spaces are ignored, and don't affect the rhythm. For example, X... X... is treated as the same rhythm as X...X...
  • Wave files using WAVE_FORMAT_EXTENSIBLE format can now be used, due to upgrading the WaveFile gem dependency to v0.8.1 behind the scenes.
  • Installing the gem is now simpler, since it no longer requires installing the legacy syck YAML parser via an extension.
  • A Fixnum is deprecated message is no longer shown when using Ruby 2.4
  • Backwards incompatible changes:
    • Song files containing a Structure section are no longer supported. A Flow section should be used instead. Support for the Structure section has been deprecated since v1.2.1 (released in 2011).
    • Track rhythms can no longer start with a | character. For example, |X...X... is no longer a valid rhythm. However, bar lines are still allowed to appear elsewhere in the rhythm. For example, X...X...|X...X...| is a valid rhythm. The reason for this change is that a rhythm starting with | is parsed as a YAML scalar block now that Beats is using the Psych YAML library behind the scenes. The fact that the old Syck YAML library didn't treat rhythms starting with a | as a YAML scalar block appears to have been a bug in Syck?
  • The minimum supported Ruby version is now 1.9.3, instead of 1.8.7

Local Development

First, install the required dependencies:

bundle install

To run Beats locally, use bundle exec and run bin/beats, to avoid using any installed gem executable. For example:

bundle exec bin/beats -v

To run the tests:

bundle exec rake test

Found a Bug? Have a Suggestion? Want to Contribute?

Contact me (Joel Strait) by sending a GitHub message or opening a GitHub issue.


Beats Drum Machine is released under the MIT license.