MIDIs, Sheet Music, and Software

Play a Piano: Imaging the Imagined
This little, virtual piano allows you to get a dose of music theory and math. Learn about how the amplitude and period of sound waves correspond with the production of pitch and volume by experimenting on this online instrument. For those who just want to create tunes, this piano is equipped with MIDI playback capabilities

The Organ Amateur Page
The site offers a number of MIDI, sheet music, and MPEG files featuring the organ. It also keeps information on famous organs, and links to more sites on how the organ works.