In music, a style of unaccompanied
close-harmony singing of sentimental ballads,
revived in the USA during the 19th century.
Traditionally sung by four male voices, since
the 1970s it has developed as a style of a
cappella choral singing for both male and
female voices. Barbershop originated in
17th-century European barber's shops, which
offered dental and medical services. Waiting
customers were provided with a cittern or
guitar by managements aware of the benefits
of music to those undergoing pain.