part song

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

• noun An unaccompanied secular, usually homophonic choral composition, especially of the 1800s.
• noun An unaccompanied secular polyphonic song predating the madrigal.

from The Century Dictionary.

• noun In music, a vocal composition for two or more independent voices or parts; loosely, a glee or madrigal, and sometimes a round or catch. Part-songs are usually meant to be sung without accompaniment.

from the GNU version of the Collaborative International Dictionary of English.

• noun A song with two or more voice parts.

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

• noun music A form of unaccompanied, often homophonic, vocal composition usually for a few voices or a small choir

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

• noun a song with two or more voice parts