海狗 (Zalophus californianus) California Sea Lion     (十页之四)
理发店形式的 和声 四人组 是美国音乐里 独特的表演方法。  http://en.wikipedia.org/wiki/Barbershop_quartet

ZT:
A barbershop quartet is a quartet of singers who sing music in the barbershop genre. It consists of a lead, the vocal part which generally carries the tune; a bass,
the part which provides the bass line to the melody; a tenor, the part which harmonizes above the lead; and a baritone, the part that completes the chord. The
baritone can sing either above or below the lead singer.

Quartets can be male or female, but are generally not mixed. A female barbershop quartet may be referred to as a Sweet Adelines quartet, and the vocal parts
have the same labels, since the roles perform similar functions in the quartet even though the vocal ranges are different.
http://www.youtube.com/watch?v=uRu3CZfteyY

请看大土佬儿组织,指挥的海狗 barbershop quartet 表演。