On page 115 we discussed the Baroque concerto and concerto grosso at the time of Bach and Vivaldi in terms of the basic concerto idea — the contest between soloist and orchestra. This basic idea was refined and sharpened by the Viennese Classical composers.

Instrumental virtuosity, in the person of the soloist, remained a central feature of the Classical concerto. At the same time, the orchestra was growing and becoming a richer expressive force. With its well-coordinated string, woodwind, and brass groups, the Classical orchestra afforded more variety than the Baroque concerto orchestra could ever do.

So the balance between the two contesting forces — solo instrument and orchestra — presented a real problem, a problem that Mozart worked out in a series of seventeen superb piano concertos written during his years in Vienna, mostly for his own concert use. (Counting earlier works, he composed twenty-seven piano concertos in all.) Mozart pitted the soloist’s greater agility, brilliance, and expressive capability against the orchestra’s increased power and variety of tone color. The contestants are perfectly matched; neither one emerges as the definite winner.

Compare the movement plan for the Classical concerto below with the symphony prototype on page 181. Concertos have long opening movements and no minuet movements.