Geophone for Hire
This instrument is a wide and shallow drum, double calf-headed and containing a small amount of lead shot or small bearings. It is very important that the shot inside the drum is rounded so it will roll around well. The player simply angles the drum and the shot inside moves. The result is a very realistic replication of the sound of the sea, ocean, channel, pond or choppy lake.
Messiaen - Des Canyons aux Etoiles