Love barbershop music.  It's normally performed by a quartet.
It's famous for it's ringing chords, produced by singing a combination of notes that are perfectly tuned.
One of the things I really love about the sound is the harmony and the use of what's called "snakes" or "swipes".
It was developed by African Americans in the late nineteenth century.
So many things were influenced by African-Americans.  They constitute 1/3 largest racial and ethnic group in the United States.
When Edison's phonograph grew in popularity, the music genre did too.
Thomas Edison
Thomas Alva Edison (February 11, 1847October 18, 1931) was an American inventor and businessman, who has been described as America's greatest inventor. He developed many devices in fields such as electric power generation, mass communication, sound recording, and motion pictures. These inventions, which include the phonograph, the motion picture camera, and the long-lasting, practical electric light bulb, had a widespread impact on the modern industrialized world. He was one of the first inventors to apply the principles of
usually sung by the tenor or baritone, except for an infrequent note or two to avoid awkward voice leading, in tags or codas, or when some appropriate embellishment can be created. One characteristic feature of barbershop harmony is the use of what is known as "snakes" and "swipes". This is when a chord is altered by a change in one or more non-melodic voices. Occasional passages may be sung by fewer than four voice parts.
Barbershop music is generally performed by either a barbershop quartet,