In music, a quartet (French: quatuor, German: Quartett, Italian: quartetto, Spanish: cuarteto, Polish: kwartet) is a method of instrumentation or vocal by 4 different sounds or voices to make a melodious music or song. A quartet can be distinguished into two parts:

1). Instrument Quartet (4 different instruments): Bass, Violin, Trumpet, Accordion.

2). Vocal Quartet for male (4 different voices): Bass, Lead, Baritone, Tenor.

Read more about Quartet:  Classical, Jazz, Popular Music, Vocal Quartet