Question: Hello Albert, My question today is:

Where did the idea of double expositions in piano concertos come from and how did it affect later compositions?

– Achilles (Malta)

Albert’s reply: As explained in Sonata Form Simplified, the first section of a movement in sonata form in the Classical era (roughly 1750–1820) as exemplified by Haydn, Mozart and Beethoven is called the exposition. The exposition states both of the main themes or (more often) theme groups.

In a concerto featuring double exposition (which eventually became the norm in the Classical period), often only the initial orchestral exposition is a full one, meaning it introduces the main themes. The solo exposition that follows is not bound by the orchestra’s themes. (It can’t be overemphasized that good musical forms are first and foremost narrative – that is, they tell a story – rather than formulaic. Only mediocre or commercial music is written according to strict formulas, the latter with commercial emphasis, like one currently famous author who wrote a bestseller by analyzing and copying the form of existing ones.)

It is tempting to assume that double expositions for instrument concertos arose from Classical sonata form, but this turns out not to be the case. After all, the two were developing concurrently, and double expositions in concertos actually predates first-movement sonata form as it became known in the Classical era:

J.S. Bach’s son Johann Christian Bach’s very first published work, the Piano Concerto in B-flat major, Op. 1, No. 1 from 1763, is (to my knowledge) the first known instance of double exposition in a concerto. The first examples of conventional Classical sonata form occurred much later, in Haydn’s String Quartets, Op. 33, which were written in 1781. Haydn said of them that they were written “in a completely new and special way,” referring to his development of sonata form as a dramatic structure.

Rather, the double exposition – in which first the orchestra and then the instrumental soloist perform two separate expositions – came about more as a development of Baroque ritornello concerto form. The term ritornello (“little return”) refers to the return of the main theme by the orchestra. The soloist played in between ritornelli, either accompanied by the orchestra or not. This development from ritornello to Classical concerto form (featuring double exposition in the first movement) is evidenced by the fact that in the latter, the soloist does not necessarily repeat the orchestra’s themes – sometimes not even the main theme.

Thus, as is common in Western music up to the 20th century, developments in musical forms were evolutionary, not revolutionary, and the change from ritornello to sonata form for the first movements (and sometimes others) of multi-movement concertos is an example of evolutionary change.

It’s important not to confuse two uses of the term “double exposition.” The term is also used for fugues that feature a full exposition (i.e., in all voices) with a new subject. Remember that the exposition of a fugue is entirely different from that of a sonata!