There are several accepted arrangements for symphony orchestra seating; however, the first violins are always to the conductor's left and the percussion in the back of the orchestra. The position of the other instruments often varies depending on the conductor's preference and the acoustical qualities of the performance space.
Generally, a full symphony orchestra has 75 to 90 members (sometimes smaller for Baroque- and Classical-period works, sometimes larger for late-Romantic, 20th or 21st century works). An orchestra is comprised of four sections: String Section - the largest group of the orchestra, with approximately 14 first violins, 12 second violins, 10 violas, 8 cellos, 8 double basses; Woodwinds - piccolo, 2 flutes, 2 oboes, English horn, 2 clarinets, bass clarinet, 2 bassoons, contrabassoon; Brass - 4 French horns, 4 trumpets, 3 trombones, tuba; Harps - 1 or 2; Percussion - timpani or kettledrums, bass and side drum, glockenspiel, triangle, cymbals, etc.
These instruments vary depending on the composer's orchestration and the conductor's interpretive decisions; certain compositions require additional instruments (according to the composer's orchestration), such as another French horn, a saxophone, supplementary percussion, a piano (not as a solo instrument, referred to as orchestra piano), an organ, etc. Also, the composer may specify fewer standard instruments than are normally employed.
The "first-chair" violinist (to the conductor's immediate left) supervises the tuning of the orchestra and is a vital liaison between the conductor and the orchestra.
The lead player of each orchestral section who is required to guide the section and who performs any solo parts written for that particular instrument.
Members of each section other than the principal.
Just before the concert begins, the orchestra tunes to the note "A" that is initially provided by the principal oboe and then supervised by the concertmaster.
Text (c) Lynne S. Mazza