GeoSID v1.0 by Scott E. Resh (October 21st, 1986) - GeoSID is a music player that can play .MUS type SIDs.  There are a few sample SIDs in the archive to test things out.  

I don't really have a category for GEOS sound related apps, so I'm putting this in the Novelty category until I run across more apps of this type.