In music, the three-key exposition is a particular kind of exposition used in

sonata form Sonata form (also ''sonata-allegro form'' or ''first movement form'') is a musical structure generally consisting of three main sections: an exposition, a development, and a recapitulation. It has been used widely since the middle of the 18th c ...

. Normally, a sonata form exposition has two main key areas. The first asserts the primary key of the piece, that is, the tonic. The second section moves to a different key, establishes that key firmly, arriving ultimately at a cadence in that key. For the second key, composers normally chose the dominant for major-key sonatas, and the

relative major In music, relative keys are the major and minor scales that have the same key signatures (enharmonically equivalent), meaning that they share all the same notes but are arranged in a different order of whole steps and half steps. A pair of major an ...

(or less commonly, the minor-mode dominant) for minor-key sonatas. The three-key exposition moves not directly to the dominant or relative major, but indirectly via a third key; hence the name.

Examples

* A very early example appears in the first movement of

Haydn Franz Joseph Haydn ( , ; 31 March 173231 May 1809) was an Austrian composer of the Classical period. He was instrumental in the development of chamber music such as the string quartet and piano trio. His contributions to musical form have led ...

's String Quartet in D major, Op. 17 No. 6: the three keys are D major, C major, and A major. (C major is prepared by a modulation to its relative minor A minor, which happens to be the dominant minor of the original key.) *

Ludwig van Beethoven Ludwig van Beethoven (baptised 17 December 177026 March 1827) was a German composer and pianist. Beethoven remains one of the most admired composers in the history of Western music; his works rank amongst the most performed of the classical ...

wrote a number of sonata movements during the earlier part of his career with three-key expositions. For the "third" (that is, the intermediate) key, Beethoven made various choices: the dominant minor ( Piano Sonata No. 2, Op. 2 no. 2; String Quartet No. 5, Op. 18 no. 5), the

supertonic In music, the supertonic is the second degree () of a diatonic scale, one whole step above the tonic. In the movable do solfège system, the supertonic note is sung as ''re''. The triad built on the supertonic note is called the supertonic ch ...

minor ( Piano Sonata No. 3, Op. 2 no. 3), and the relative minor ( Piano Sonata No. 7, Op. 10 no. 3). Later, Beethoven used the supertonic major ( Piano Sonata No. 9, Op. 14 no. 1, Piano Sonata No. 11, Op. 22), which is only a mild sort of three-key exposition, since the supertonic major is the dominant of the dominant, and commonly arises in any event as part of the modulation. As he entered his so-called "middle period," Beethoven abandoned the three-key exposition. This was part of a general change in the composer's work in which he moved closer to the older practice of

, writing less discursive and more closely organized sonata movements. *

Franz Schubert Franz Peter Schubert (; 31 January 179719 November 1828) was an Austrian composer of the late Classical and early Romantic eras. Despite his short lifetime, Schubert left behind a vast ''oeuvre'', including more than 600 secular vocal wor ...

, who liked discursive forms for the entirety of his short career, also employed the three-key expositions in many of his sonata movements. A famous example is the first movement of the

Death and the Maiden Quartet The String Quartet No. 14 in D minor, D 810, known as ''Death and the Maiden'', is a piece by Franz Schubert that has been called "one of the pillars of the chamber music repertoire". It was composed in 1824, after the composer suffered a ...

in D minor, in which the exposition moves to F major and then A minor (translated to D major and minor respectively in the recapitulation), a formula that is repeated in the final movement; another is the Violin Sonata in A major (in which the second theme appears in G major and B major, while only the closing passage of the exposition is in the dominant, E major). His B major piano sonata, D 575, even uses a four-key exposition (B major, G major, E major, F-sharp major): this key scheme is literally transposed up a fourth for the recapitulation. The finale of his sixth symphony (D 589) is an even more extreme case: its exposition passes from C major to G major by way of A-flat major, F major, A major, and E-flat major, making a six-key exposition. *

Felix Mendelssohn Jakob Ludwig Felix Mendelssohn Bartholdy (3 February 18094 November 1847), born and widely known as Felix Mendelssohn, was a German composer, pianist, organist and conductor of the early Romantic period. Mendelssohn's compositions include sy ...

followed the Death and the Maiden example in the first movement of his second Piano Trio, in which the E flat major second theme gives way to a G minor close (transposed to C major and minor in the recapitulation). * The first movement of

Frédéric Chopin Frédéric François Chopin (born Fryderyk Franciszek Chopin; 1 March 181017 October 1849) was a Polish composer and virtuoso pianist of the Romantic period, who wrote primarily for solo piano. He has maintained worldwide renown as a leadin ...

's Piano Concerto in F minor also has a three-key exposition (F minor, A-flat major, C minor). * The first movement of the second cello sonata by

Brahms Johannes Brahms (; 7 May 1833 – 3 April 1897) was a German composer, pianist, and conductor of the mid-Romantic period. Born in Hamburg into a Lutheran family, he spent much of his professional life in Vienna. He is sometimes grouped with ...

also employs a three-key exposition moving to C major and then A minor, the exposition of the first movement of the String Sextet in B flat involves an intervening theme in A major before reaching F, and the Piano Quartet in G minor involves secondary themes in D minor and major respectively (the first of these being omitted in the recapitulation and the second transposed to E flat major moving back to G minor). The D minor violin sonata has a final movement that moves through a calm second theme in C major before closing the exposition in A minor.

Examples

Further reading