My dad used to sing in a barbershop quartet!  I loved listening to it!  
Oh really? That is really interesting. I didn't know those even existed. Did they use instruments?  
Nope. I think the point of barbershop is that is a capella.  But I could be wrong.  Do you know?
I think they would sometimes use instruments like the piano
Hmm..Interesting.  My dad's group did not use instruments.  How long have barbershop quartets been around, do you know?
It started during the 1930's during the barbershop revival era. 
Well that makes sense.  Is it always men, or can women sing, too?
Females can sing too. I think quartets are generally all male or all female.