An elixir-based synthesizer. To use it, you can evaluate:

QuickieSynth.Sound.play("C")

If you want to build a composition, you can do that like so:

QuickieSynth.Composition.play(100, "CEGCEGAAB")

To run the keyboard UI, evaluate the following:

QuickieSynth.UI.start

Then click in the window and play with the bottom two rows of your keyboard.