The Exposition serves two main purposes which are :

The Exposition serves two main purposes which are
 
  A) to let all of the instruments play at once and to get the attention of the audience
 
  B) to establish the basic character of the movement and to create the musical idea that is to be worked out
 
  C) to establish that the work is in sonata form and to present a contrast of keys
 
  D) to create a harmonic tensions that is to be worked out through the movement, and to establish the significance of the solo instrument
 
  E) to take up about fifteen minutes of time and to establish a tempo for the movement