The orchestra may be regarded as a large instrument capable of making a great number of different sounds simultaneously or successively. Its power is limited or enormous depending on whether it involves all or only a part of the means of execution at the disposal of modern music and on whether these means are well or badly chosen and well or badly located in acoustical conditions of greater or lesser advantage.

The assortment of players whose coming together constitutes an orchestra could be regarded as its strings, tubes, chests and surfaces, made of wood or metal – machines bearing intelligence but subordinate to the action of an immense keyboard played by the conductor following the directions of the composer.

I think I have already said that one cannot show how beautiful orchestral effects are made and that this skill, which must clearly be developed by practice and reasoned observation, is like skill in melody, expression and even harmony: one of the precious gifts that the musician-poet, the inspired originator, can only be given by nature. But it is certainly straightforward to demonstrate with some precision the art of training orchestras to give faithful renderings of compositions of all shapes and sizes.

A distinction must be made between theatre orchestras and concert orchestras. The first are in general inferior to the second in many ways.