violin

viulu puhekieltä A musical four-string instrument, generally played with a bow or by plucking the string, with the pitch set by pressing the strings at the appropriate place with the fingers; also any instrument of the https://en.wikipedia.org/wiki/Violin_family violin family.
(RQ:Wodehouse Offing)
puhekieltä A violinist.

The first violin often plays the lead melody lines in a string quartet.