Quartet

Noun

1. A group of four people or things, particularly A group of four musicians who perform classical music together.

   "The string quartet played some chamber music."

2. A group of four musicians who perform classical music together.

   "The string quartet played some chamber music."

3. A musical composition in four parts, each performed by a single voice or instrument.

   "He composed a string quartet."

4. A group of four singers, usually males, who sings together in four-part harmony.

   "The barbershop quartet performed the composition a cappella."