A piano concerto is a type of concerto, a solo composition in the Classical music genre which is composed for a piano player, which is typically accompanied by an orchestra or other large ensemble. Piano concertos are typically virtuoso showpieces which require an advanced level of technique on the instrument, including melodic lines interspersed with rapid scales, arpeggios, chords, complex contrapuntal parts and other challenging material. When piano concertos are performed by a professional concert pianist, a large grand piano is almost always used, as the grand piano has a fuller tone and more projection than an upright piano. Piano concertos are typically written out in music notation, including sheet music for the pianist (which they typically memorize so that they can play the concert without sheet music), orchestra parts for the orchestra members, and a full score for the conductor, who leads the orchestra in the accompaniment of the soloist.
Depending on the era in which a piano concerto was composed, the orchestra parts may provide a fairly subordinate accompaniment role, setting out the bassline and chord progression over which the piano plays solo parts (more typical during the Baroque music era, from 1600 to 1750 and the Classical music period, from 1730 to 1800), or the orchestra may be given an almost equal role to the piano soloist, with orchestra instrumentalists and sections introducing key musical themes and playing virtuostic parts for their instruments and in which there is a "dialogue" or "conversation" between the piano soloist and the orchestra. When music students and music competition auditionees play piano concertos, the orchestra part may be performed in an orchestral reduction, a conversion of the orchestra parts into a part for an accompanist playing piano or pipe organ, as it is very expensive to hire a full orchestra. Keyboard concerti were common in the time of Johann Sebastian Bach in the Baroque music era, during the Classical music period and during the Romantic music era (1800-1910). Keyboard concertos are also written by contemporary classical music composers. Twentieth- and 21st-century piano concertos may include experimental or unusual performance techniques. In the 20th and 21st century, J.S. Bach's harpsichord concertos are sometimes played on piano. There are variant types of piano concertos, including double piano concertos, for two solo pianists and orchestra, and double or triple (or larger solo groups) concertos in which the piano soloist is joined by a violinist, cellist, or another instrumentalist.
Well-known examples from the middle to late Romantic era include concertos by Edvard Grieg, Johannes Brahms, Camille Saint-Saëns, Franz Liszt, Pyotr Ilyich Tchaikovsky, and Sergei Rachmaninoff. Antonín Dvo?ák and Franz Xaver Scharwenka wrote some lesser-known concertos during this time. Edward Elgar made sketches for a piano concerto but never completed it. In the 19th century, Henry Litolff blurred the boundary between piano concerto and symphony in his five works entitled Concerto Symphonique, and Ferruccio Busoni added a male choir in the last movement of his hour-long concerto. Wilhelm Furtwängler wrote his Symphonic Concerto for Piano and Orchestra, which lasts more than one hour, in 1924-1937. In a more general sense, the term "piano concerto" could extend to the numerous often programmatic concerted works for piano and orchestra from the era - Beethoven's Choral Fantasy, Liszt's Totentanz and Ruins of Athens Variations, and Richard Strauss's Burleske are only a few of the hundreds of such works. The few well-known piano concertos that dominate 20th-century and 21st-century concert programs and discographies comprise only a small part of the repertoire that proliferated on the European music scene during the 19th century.
The piano concerto form survived through the 20th century into the 21st, with examples being written by Leroy Anderson, Milton Babbitt, Samuel Barber, Béla Bartók, Arthur Bliss, York Bowen, Benjamin Britten, Elliott Carter, Carlos Chávez, Peter Maxwell Davies, Emma Lou Diemer, George Gershwin, Alberto Ginastera, Ferde Grofé, Aram Khachaturian, György Ligeti, Magnus Lindberg, Witold Lutos?awski, Gian Francesco Malipiero, Frank Martin, Bohuslav Martin?, Nikolai Medtner, Peter Mennin, Peter Mieg, Selim Palmgren, Dora Peja?evi?, Willem Pijper, Sergei Prokofiev, Behzad Ranjbaran, Maurice Ravel, Arnold Schoenberg, Peter Sculthorpe, Dmitri Shostakovich, Roger Smalley, Arthur Somervell, Igor Stravinsky, Heinrich Sutermeister, Alexander Tcherepnin, Michael Tippett, Ralph Vaughan Williams, Heitor Villa-Lobos, Pancho Vladigerov, Charles Wuorinen, and others. Parts of other 20th-century symphonic works give the piano occasional prominence like any other instrument of the orchestra, as in the Symphony in Three Movements by Igor Stravinsky, Samuel Barber's violin concerto, all six symphonies of Bohuslav Martin?, and the Symphony No.3 by Michael Tippett.
The German Paul Wittgenstein lost his right arm during World War I, and on resuming his musical career asked a number of composers to write pieces for him that required the left hand only. The Czech Otakar Hollmann, whose right arm was injured in the war, did likewise but to a lesser degree. The results of these commissions include concertante pieces for orchestra and piano left hand by Bortkiewicz, Britten, Hindemith, Janá?ek, Korngold, Martin?, Prokofiev, Ravel, Franz Schmidt, Richard Strauss, and others.
Concertos and concert works for two solo pianos were written by Bach (two to four pianos, BWV 1060-65, actually harpsichord concertos, but often performed on pianos), Mozart (two, K 242 (originally for three pianos and orchestra) and K 365), Mendelssohn (two, 1823-4), Bruch (1912), Béla Bartók (1927/1932, a reworking of his Sonata for two pianos and percussion), Poulenc (1932), Arthur Bliss (1924), Arthur Benjamin (1938), Peter Mieg (1939-41), Darius Milhaud (1941 and 1951), Bohuslav Martin? (1943), Ralph Vaughan Williams (c. 1946), Roy Harris (1946), Gian Francesco Malipiero (two works, both 1957), Walter Piston (1959), Luciano Berio (1973), and Harald Genzmer (1990). Apart from the Bach and Mozart examples, works for more than two pianos and orchestra are considerably rarer, but have been written by Morton Gould (Inventions for four pianos and orchestra, 1954), Peter Racine Fricker (Concertante for three pianos, timpani, and strings, 1956), Wolfgang Fortner (Triplum for three pianos and orchestra, 1966) and Georg Friedrich Haas (limited approximations for six microtonally tuned pianos and orchestra, 2010)
A classical piano concerto is often in three movements.
Examples by Mozart and Beethoven follow this model, but many others do not. Beethoven's fourth concerto includes a last-movement cadenza, and many composers introduced innovations. Liszt's concertos are played without a break, though separate movements are clearly evident. One example of a concerto in only one discrete movement (Allegro brillante) is Tchaikovsky's Piano Concerto No. 3 in E-flat major (1893).