Question: I am confused about sonatas. I've read that sonata is a single-movement piece, but others say that it has several movements... or was it only a single movement earlier on and then changed into multi-movement?
And just confirming, a sonata form is just one movement in a sonata, and has three sections, the expo, develop and recap?Joanna (Australia)
Albert's reply: Confusion about the definition and form of sonatas is entirely understandable. The meaning of the term changed over the centuries and it indeed refers to all of the above.
The word derives from the Italian sonare, which means "to sound." It refers to an instrumental piece—one played by instruments rather than sung. A sonata is played, whereas a cantata—derived from the Italian cantare meaning "to sing"—is sung.
Initially, in the Baroque era (roughly 1600-1750, ending with the death of Bach), sonatas could be for one or several instruments. The term was used especially for solo compositions for keyboard or violin. They could be single-movement works (such as Domenico Scarlatti's keyboard sonatas, always in A B A' B' form) or multi-movement (such as J. S. Bach's sonatas for solo violin).
In the Classical era (roughly 1750-1825, from around the birth of Mozart to the death of Beethoven), the term was used for multi-movement works for solo piano or a solo melody instrument (violin, flute, cello, etc.) with piano accompaniment.
Usually only the first movement of a multi-movement work titled "sonata" in the Classical era is in sonata form. I explain Classical-period sonata form in some detail in the article Sonata Form Simplified, with its four major sections: exposition, development, recapitulation, coda.
The first movement (and sometimes others as well) of a Classical symphony is also in sonata form. A symphony is thus like a sonata for orchestra rather than solo instrument(s). The article Sonata Form and Symphonic Form offers additional detail.
In the Romantic era (roughly 1825-1900), composers continued to experiment with sonata form. Franz Schubert created a "sonata within a sonata" with his ingenious "Wanderer" Fantasy for piano, in which four distinct movements are rolled into one, and each of them is based on the same theme. Franz Liszt's Piano Sonata in B minor uses Schubert's compositional technique, developing it even further.
In the 20th century and beyond, sonatas returned to their original, flexible meaning. Now, the term is applied to single- or multi-movement works for solo instrument(s).
Charles Rosen's book Sonata Forms is a definitive reference work, and there are many excellent books on the subject.