premise: Backing vocalists provide vocal harmony.
hypothesis: Backing vocalists are singers who provide vocal harmony with the lead vocalist or other backing vocalists . The style of singing used by backup singers varies according to the type of song and the genre of music the band plays . In pop and country songs , backup vocalists may perform vocal harmony parts to support the lead vocalist . In hardcore punk or rockabilly , other band members who play instruments may sing or shout backup vocals during the chorus ( refrain ) section of the songs .