There are a number of other types of quartets, two of the more common ones you may come across are the wind quartet and the vocal quartet.
Often a wind instrument (eg. flute, oboe, clarinet, bassoon) will replace one of the violins (the first) – so the line up would be
Or they can be made up of four wind instruments
Largo “From the New World”
A vocal quartet Is made up of four singers:
These vocal quartets can be acapella (without any instruments) or accompanied by instruments.
Vocal quartets can also appear as part of larger musical compositions like symphonies, or operas.