What is the instrument-playing leader of the orchestra called?

The concertmaster is the leader of the first violin section in an orchestra (or clarinet, oboe, flute in a concert band) and the instrument-playing leader of the orchestra. After the conductor, the concertmaster is the second-most significant leader in an orchestra, symphonic band or other musical ensemble. Another common term in the U.S. is "first chair." In the U.K., the term commonly used is "leader."

The concertmaster sits to the conductor's left, closest to the audience, in what is called the "first chair," "first stand" or outside of the US "first desk." The concertmaster makes decisions regarding bowing and other technical details of violin playing for the violins, and sometimes all of the string players. They lead the orchestra in tuning before concerts and rehearsals, and other technical aspects of orchestra management.

Leading the orchestral tuning is not a mere formality; if the concertmaster believes that a section is not adequately tuned, they will signal to the oboe player to play another "A." Several larger orchestras have one or more assistant concertmasters, who lead the orchestra in the concertmaster's absence.