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What is the difference musically between sonata and fugue?
July 24, 2013 8:25PM
Both are forms frequently but not exclusively used for solo instruments. Sonatas are compositions of anywhere from 2 to 3 or 4 independent sections that follow various conventions of structure, rhythm and tempo depending on the time and place of composition. Some sections will usually be based on various dance forms and the internal structures of these sections may be more rondo-like or repetitive as are songs; other sections will be written in what is called sonata-form, which is a distinct concept from sonata. Sonata-form is an approach to musical material that was a significant part of the development of symphonic music. It involves the exposition of thematic material, its development melodically and rhythmically, and its interplay with other materials introduced later on. There is then a recapitulation, a coda and a conclusion. Broadly, the best sonatas can be seen as miniature symphonies.
Sections written in sonata-form (I'm speaking as a passionate lay person and not an expert) by a skillful composer have characteristics that sometimes seem magical, if they are attended to by the listener. Anyone who has tried writing something as simple as a song, with a standard "song" structure, and has discovered how difficult that really is (I should say that it's really difficult to write an excellent song) will appreciate the nature of symphonic writing. Consider the opening of Beethoven's Eroica, Pastoral, and the 9th, or practically anything by Mahler. The music progresses with perfect coherence, and the sense is that not so much as one note could be changed without wrecking the entire structure, and yet it is not a song as such. Theme falls upon theme, and themes repeat and interplay with newly introduced material. When I think about writing something, my ear jumps at the chance to finish up with a 5-1 cadence and get on with it. As a result I think that sonata-form can be much more like abstract impressionism than anything else (early Pollock?), with clear, coherent structures balanced perfectly against each other, but seemingly by magic, not by some pre-ordained formula. It is said of Beethoven that he possessed every musical gift except the gift of melody [source?]. OK, he may not have been great at writing popular ditties. The statement highlights that he could create something magnificent out of very nearly nothing. Case in point: da da da daaaaaaaa...
Fugues are almost always single sections or pieces of music, and are usually identified by the number of voices that the fugue will contain. While non-fugue forms often are structured as melodic material supported by harmony underneath it, and with various devices of rhythm and counterpoint added to develop interest, complexity or other kinds of effect, the concept of fugue usually is that the voices are co-equal and co-functional. Voices will enter one by one, (for example, the alto line may introduce the theme, followed by soprano with the theme coming in a 5th above the alto, then tenor and bass in turn, at various degrees depending on the composer's desire.) Each voice opens with the original theme until all the voices are singing together. There are many techniques to varying and blending the voices and thematic material. Voices can rest from time to time, and when they re-enter, it will sometimes be with a re-statement of the theme. Fugues can move from major to minor mode, the theme can be inverted, the time-frame of the theme can be stretched out in one voice (in the bass for example, where it might present as a slower, solid basis for voices above moving at varying rates). While sonatas and symphonies can exhibit much more freedom in the voicings of various harmonies and developmental passages, the best fugues always maintain the voice structure they start with, and the sense of a beautiful, well-written fugue is that by the end, the voices have gone to the very depths of the theme, have examined it in the most meaningful way and have left nothing wanting by the time the last note sounds. The harmony and counterpoint are almost (or so it seems) spontaneously discovered as the voices interact.
Refer to any fugues by Bach, or for some more recent examples: the fugue in Ravel's Tombeau de Couperin, or the fugue passages from Stravinsky's Symphony of Psalms.