The Bazantar:
The Bazantar is a relatively new creation, invented by Mark Deutsch (pictured above). Its essentially a 5 string upright accoustic bass, but with 33 strings added, 29 sympathetic strings and 4 drone strings. Adding a whole new sound and texture to the classical instrument.
The sympathetic strings range spans at 4 octaves, but the instrument itself has an impressive 5 octave range. When the melodic, sympathetic and drone strings are played together, it creates a very rich, complex soundscape.
YouTube - Mark Deutsch Playing the Bazantar
Demonstration by Deutsch.
http://www.oddmusic.com/clips/bazantar.mp3
Sound clip.