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Platform independent realtime MIDI input and output for Ruby.

Also see micromidi which builds a full MIDI messaging DSL on top of unimidi


  • Supports Linux, JRuby, OSX, Windows and Cygwin

  • No compilation required

  • Both input and output to and from multiple devices concurrently

  • Agnostically handle different MIDI and SysEx Message types

  • (OSX Only) Use IAC to internally route MIDI to other programs


Using Ruby 1.9.2 or JRuby 1.6.1 (or newer) is strongly recommended. JRuby should be run in 1.9 mode

One of the following libraries is required based on what platform you're using. It should install automatically with the unimidi gem. In some uncommon cases, they will all install



gem install unimidi


Blog Posts

In addition, some examples are included with the library


There are a set of tests which assume that an output is connected to an input. You will be asked to select which input and output as the test is run.

The tests can be run using

rake test

See below for additional notes on testing with JRuby


Platform Specific Notes


  • You must be in 1.9 mode. This is normally accomplished by passing –1.9 to JRuby at the command line. For testing in 1.9 mode, use

    jruby --1.9 -S rake test
  • javax.sound has some documented issues with SysEx messages in some versions OSX Snow Leopard which do affect this library.


  • libasound and libasound-dev packages are required


Ari Russo <ari.russo at>


Apache 2.0, See the file LICENSE

Copyright © 2010-2011 Ari Russo

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