Create and analyze musical pitches from MIDI names/numbers and scientific pitch notation (SPN)..

Control VLC Media Player with MIDI

Filter Program Change (PC) or Control Change (CC) events from MIDI files.

A Ruby library to send manufacturer-specific or instrument-specific MIDI messages

Convert a note string to MIDI note number.

== Midi experiments

compile a Music Macro Language file to a Standard MIDI file.

Control MPlayer with MIDI

KuroMusic is midi controll library writed by ruby.

Ruby bindings for OS X's high-quality music sequencing/live-play API

Quick and easy prototyping for Arduino-based MIDI pedalboards

Universally patch controller messages such as MIDI and OSC between devices

Peas defines constants from music theory and allows one to perform math with them. Currently supports pitches (as MIDI values), pitch classes, and intervals using semitones, wholetones, chromatic, latin or diatonic abbreviations.

Ruby/IFF is a Ruby library for loading and serializing file formats based (more or less loosely) on the IFF standard; these include many popular file formats like MIDI and WAV

Stretto is a Ruby implementation of JFugue, an open source library originally written in Java by David Koelle for programming MIDI.