Silophone. Play sound into a silo.
That's right. Upload a .wav or .mp3 file (1 mb max) and it plays into an old silo in Montreal. You can listen to it via RealAudio.

From the web site:
Silophone makes use of the incredible acoustics of Silo #5 by introducing sounds, collected from around the world using various communication technologies, into a physical space to create an instrument which blurs the boundaries between music, architecture and net art. Sounds arrive inside Silo #5 by telephone or internet. They are then broadcast into the vast concrete grain storage chambers inside the Silo. They are transformed, reverberated, and coloured by the remarkable acoustics of the structure, yielding a stunningly beautiful echo. This sound is captured by microphones and rebroadcast back to its sender, to other listeners and to a sound installation outside the building. Anyone may contribute material of their own, filling the instrument with increasingly varied sounds.
Play the Silophone