Classical Concerto

The Classical concerto is a three-movement work for a solo instrument (most often piano, violin, cello or wind) and orchestra. The first movement is in a double-exposition sonata form: the orchestra introduces the themes alone, then restates them with the soloist's elaboration; a development section follows, then a recapitulation. The cadenza, a quasi-improvised solo passage near the end of the first (and sometimes third) movement, was originally improvised by the soloist on stage. The slow second movement is lyrical and aria-like; the finale is a rondo, dance-like and bright. Orchestras are small by later standards — strings plus pairs of winds and horns, occasionally trumpets and timpani — and the soloist functions both as protagonist and as virtuoso ornament-bearer.

The concerto's Baroque ancestor was the concerto grosso (Corelli, Handel) and the solo concerto (Vivaldi, J.S. Bach). The Classical reformulation was achieved primarily by Mozart, whose twenty-three piano concertos (composed 1773-1791, with the late Vienna concertos K. 466, 488, 491 and 503 as the high-water mark) defined what the form could do. Haydn wrote keyboard, cello, trumpet and horn concertos. Beethoven's five piano concertos (1795-1809) and single violin concerto (1806) extended the form harmonically and dramatically while keeping the Classical layout. The twentieth century continued to revisit the model.

The double exposition is the form's signature design: hear how the same material sounds different when the orchestra plays it alone versus when the soloist takes it over. The cadenza is the structural crux — modern performers usually play composed cadenzas (Mozart's own where they survive, otherwise Beethoven's or a later editor's), but the moment of solo-against-orchestra suspension is the same. Listen too for the dialogue: in Mozart's late concertos a wind instrument (clarinet, bassoon, oboe) often becomes a second soloist, trading phrases with the keyboard.

Mozart's Piano Concerto No. 21 in C major, K. 467 (1785) — the slow movement, made famous by the 1967 film 'Elvira Madigan,' is one of the most-played classical pieces anywhere. For the more dramatic side, the Piano Concerto No. 20 in D minor, K. 466 (1785). Murray Perahia's complete Mozart concerto cycle is a sound complete reference.

Mozart usually wrote his piano concertos to play himself, with the cadenzas left blank or improvised on the night. Only a fraction of his original cadenzas survive — most modern performances of the unaccompanied moments use his nephew's or later editors' reconstructions.