Updated: Jul 24, 2020
Overtures can be long or short, loud or soft, melodious or dissonant; they can be anything. Following the classical era of rules and structures, when composition became less regulated, the art of the overture became even freer.
Overtures are very important to an opera. This is, in large part, because overtures sometimes introduce snippets of the opera itself. Listening to a Wagner overture -- Tannhäuser, Dutchman, and Meistersinger, in particular -- and knowing that the opera is simply an extended version of the overture is a very nice thing. Not all overtures, however, function in this way. Some overtures are completely separate pieces of music, independent of the opera. Rossini's 'Il Barbiere di Siviglia' is a good example of this. In operas of the 18th century, composers would often use movements of symphonies as overtures for their operas. Mozart is an example of a composer who didn't use his overtures to introduce themes of the opera. The idea of overtures containing music from the opera began in Italy. Rossini did this in the overture of his opera 'Semiramide', amongst others.
Shorter overtures, usually referred to as 'preludes', typically lasting around 3-4 minutes, can function either way. The prelude to 'La Traviata' is very short, yet it introduces a key theme to the opera, unlike the prelude to 'Aida' which is its own little piece.
The title of this article may be misleading, for Puccini's operas lack overtures entirely. His operas dive straight into the action. Interestingly, Wagner's operas, like Puccini's, are technically supposed to go straight from the overture to the drama non-stop, and yet Wagner's overtures last over 10 minutes on average and are regular concert repertoire. Puccini didn't compose full preludes or overtures.
It is not as if every composer of opera has a specific style used for all of their operas. Verdi wrote operas with 10-minute overtures, operas with 3-minute preludes, and operas, in some cases, with no overture at all. Some of his operas have overtures that transition straight into the opera, while others have stops between the overture and the opera.
Overtures can be anything. They can be 15 minutes long or 1 minute long, and can be used to introduce the opera's music or just as independent music that precedes the action.
Overture to 'Tannhauser'. An example of a long overture that introduces the opera's themes:
June 21, 2020