Procedural music editor - http://www.automatune.com/
Easy procedural music
Automatune is an easy-to-use procedural music editor that doesn’t require any coding or special knowledge. The name Automatune comes from the word “automaton”, which means “a machine designed to automatically follow a predetermined sequence of operations or respond to encoded instructions”. Automatune is an automaton that makes tunes!
When you add arrows and notes to the Automatune grid, the dots will follow the arrows, playing any notes they encounter along the way. Automatune has customizations for grid size and tempo, and even lets you share your creations by URL or by saving them to a file.
Automatune is open source and licensed under GPL.