jug band

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A group that uses unconventional or improvised instruments, such as jugs, kazoos, and washboards.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun music Especially in the U. S., a group of rustic musicians, specializing in bluegrass or folk music, whose instruments include empty jugs, bottles, and similar containers of various sizes which produce musical sounds when the player blows across the openings at the tops of their necks.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun a musical group that uses jugs and washboards and kazoos and other improvised instruments