First violin

The Concertmaster (from the German Konzertmeister) is the second-most significant person in an orchestra, symphonic band or other musical ensemble after the conductor or director. Another common term in the U.S. is "First Chair." In the U.K., the term commonly used is "leader."

In an orchestra, the concertmaster is the leader of the first violin section. There is another violin section, the second violins, led by the principal second violin. Any violin solo in an orchestral work is played by the concertmaster (except in the case of a concerto, in which case a guest soloist usually plays). It is usually required that the concertmaster be the most skilled musician in the section, experienced at learning music quickly, counting rests accurately and leading the rest of the string section by his or her playing and bow gestures.

The concertmaster sits to the conductor's left, closest to the audience, in what is called the "first chair," "first [music] stand" or "first desk" (in the UK or sometimes elsewhere). (In one instance, Ferdinand David had been concertmaster of the Leipzig Gewandhaus Orchestra since Felix Mendelssohn became conductor in 1835. In 1847 Joseph Joachim joined David on the 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. He or she leads the orchestra in tuning before concerts and rehearsals, and other technical aspects of orchestra management. Leading the orchestral tuning is not just a mere formality; if the concertmaster believes that a section is not adequately tuned, he or she 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.

The concertmaster, along with the conductor and section principals, will normally participate in the auditions of important musicians (e.g., principal players) in the orchestra.

...
Wikipedia