The term 'Barbershop Call' is a type of vocal harmony that is typically performed by four male singers. It is characterized by close harmonies and a unique style of singing. The term 'NEXT' is a 4 letter word that is often used to describe the NEXT step in a process or the following part of a sequence. In the context of Barbershop Call, it could refer to the NEXT part of the song or the NEXT singer in the group.