didnt know Barbershop music was a category of music.
Oh yes, it's a vocal harmony codified during the barbershop revival era. It's mostly a cappella
oh ok, seems kind of a dead art tho.
Oh, yes, it is a dying breed. But when it was in full swing it was mostly played by a barbershop quartet, a group of four singers.
Oh so barbershop quartets that makes sense, thought it was more inline of something like elevator music but it means quartets
Oh, yes the quartets usually have a lead, a bass, a tenor, and a baritone. They all harmonize together to entertain barber patrons. 
Oh yea thats really cool.
Isn't it though? Too bad most of them have died out, you might be lucky to find a female barbershop quartet somewhere, usually referred to as Sweet Adelines quartets.
what a weird name that is haha.
Yes, believe it or not there's still 21,000 members of the "Sweet Adelines Internation", a worldwide organization of women singers.