January 19, 2011
In the Classical period, a concerto gave a composer the opportunity to show off not only his orchestral writing, but also his chops as a performer. It was customary for composers to premiere their new concertos (piano concertos outnumbering other kinds) with as much pomp and flair as possible. When Mozart wrote the concerto on this weekend’s program, Concerto No. 20, he was an active soloist, earning revenue from subscription concerts. He soon turned to writing operas, putting concertos on the backburner, but in the early 1780s, the concerto was Mozart’s bread and butter.
The first movement of a concerto (there are usually three) is structured in such a way so that the soloist will have plenty of opportunities to show off the ability to play, to interact with the orchestra, and most importantly, to improvise. The movement usually begins with the presentation of themes. This “exposition,” as it is called, is carried out by the orchestra while the soloist remains silent. The mere presence of the soloist, just sitting there not doing anything, ratchets up the anticipation. It’s almost like putting a wrapped package on a table, but not allowing anyone to open it for a while.
The orchestra often presents two themes while the soloist waits. This opening gambit is similar to the way symphonies begin, although there is an important difference: in a symphony, the second theme is in a new key. In a concerto, the orchestra gives us two themes and both of them stay in the same key. Why do they do this? So that when the soloist in a concerto finally comes in, the orchestra will still be playing in the same key that the piece started in. Then, during the soloist’s “exposition” of the same themes, he or she will take us to a new key. Since there are essentially two expositions, we call the structure of this movement “double-exposition form.”
After both the orchestra and the soloist get a shot at presenting the themes, the two entities in the concerto enter into what is known as the “development.” In this section, soloist and orchestra bandy themes back and forth, decorate what’s already been presented, or break down the established themes into smaller and smaller parts. The soloist gets an opportunity here to show off by giving us highly decorated versions of the themes or taking us on flights of fancy while the orchestra keeps us grounded.
The opening themes return in the “recapitulation,” but this time, both soloist and orchestra play together. Before the movement can end, however, there is one more important aspect: the cadenza. A cadenza is a long passage for only the soloist. It was customary for performers to improvise the cadenza on the spot, and Mozart—we know from contemporary accounts—was a master at this skill. The cadenza is of no set length, and a player could really go to town with impressive runs and quick finger work. There is a signal—the soloist plays a trill on a particular harmony—to let the conductor and the orchestra know that the soloist is finished. Once all parties are back in and playing, it’s only a short time until the movement is over. It’s a fascinating musical journey, and there are still two more movements to go!
Mozart’s Piano Concertos, like this one, may have influenced later composers of this genre. Beethoven actually wrote down and published his own cadenza for this very concerto (for those performers who weren’t such great improvisers). Beethoven wrote solo piano literature for the advancement of his own career, but of course, that part of his career was cut short by his deafness. While he was writing pieces that he could perform, however, Beethoven tweaked the double exposition form a bit, putting his own spin on things. Other composers also made their own contributions to the genre. The form, like anything else, evolved with the passage of time.
Mozart’s concertos are wonderful for many reasons, but one of the most important, in my humble opinion, is that they manage to be great exemplars of traditional form and yet sound fresh and inventive. He could do that. He’s Mozart, after all.