A full symphony orchestra may include over 100 musicians. It is a very powerful and versatile ensemble, capable of expressing an enormous variety of tone-colours, dynamics and textures.

The orchestra has 4 main sections, Strings, Woodwind, Brass, and Percussion.

The layout of the modern orchestra is fairly standardized, although some conductors may decide to change it around to suit their individual ideas. In the conventional layout, the strings are at the front, because they are not as loud as the woodwind or especially, as the brass. The first violins are at far left, they usually play the top line of the strings score. The second violins are next to the first violins, going to the right. Then come the violas, either at the centre, or just to right of centre. The cellos are on the right, and lastly, the double-basses are at the extreme right side of the stage. The woodwind consists of flutes, oboes, clarinets and bassoons, arranged in the centre, behind the strings. The brass are behind the woodwind, with the French Horns at left, trumpets at centre, then trombones and a tuba on the right. The percussion section is right at the back.

Early orchestras were led by the most senior (or most talented) first violinist, who would give occasional directions to the rest of the orchestra with his bow. This player is still called the leader of the orchestra today. However, most modern large orchestras today have a conductor, who stands in front of the orchestra using his hand and a baton to show the tempo, and to give entry cues to some players, and to indicate the dynamics.