Neoclassicism in music was a twentieth-century trend, particularly current in the interwar period, in which composers sought to return to aesthetic precepts associated with the broadly defined concept of "classicism", namely order, balance, clarity, economy, and emotional restraint. As such, neoclassicism was a reaction against the unrestrained emotionalism and perceived formlessness of late Romanticism, as well as a "call to order" after the experimental ferment of the first two decades of the twentieth century. The neoclassical impulse found its expression in such features as the use of pared-down performing forces, an emphasis on rhythm and on contrapuntal texture, an updated or expanded tonal harmony, and a concentration on absolute music as opposed to Romantic program music.

In form and thematic technique, neoclassical music often drew inspiration from music of the eighteenth century, though the inspiring canon belonged as frequently to the Baroque (and even earlier periods) as to the Classical period—for this reason, music which draws inspiration specifically from the Baroque is sometimes termed neo-Baroque music. Neoclassicism had two distinct national lines of development, French (proceeding partly from the influence of Erik Satie and represented by Igor Stravinsky, who was in fact Russian-born) and German (proceeding from the "New Objectivity" of Ferruccio Busoni, who was actually Italian, and represented by Paul Hindemith). Neoclassicism was an aesthetic trend rather than an organized movement; even many composers not usually thought of as "neoclassicists" absorbed elements of the style.

Although the term "neoclassicism" refers to a twentieth-century movement, there were important nineteenth-century precursors. In pieces such as Franz Liszt's À la Chapelle Sixtine (1862), Edvard Grieg's Holberg Suite (1884), Pyotr Ilyich Tchaikovsky's divertissement from The Queen of Spades (1890), George Enescu's Piano Suite in the Old Style (1897) and Max Reger's Concerto in the Old Style (1912), composers "dressed up their music in old clothes in order to create a smiling or pensive evocation of the past".

Sergei Prokofiev's Symphony No. 1 (1917) is sometimes cited as a precursor of neoclassicism. Prokofiev himself thought that his composition was a "passing phase" whereas Stravinsky's neoclassicism was by the 1920s "becoming the basic line of his music". Richard Strauss also introduced neoclassical elements into his music, most notably in his orchestral suite Le bourgeois gentilhomme Op. 60, written in an early version in 1911 and its final version in 1917.

Ottorino Respighi was also one of the precursors of neoclassicism with his Ancient Airs and Dances Suite No. 1, composed in 1917. Instead of looking at musical forms of the eighteenth century, Respighi, who, in addition to being a renowned composer and conductor, was also a notable musicologist, reached back to Italian music of the sixteenth and seventeenth centuries. His fellow contemporary composer Gian Francesco Malipiero, also a musicologist, compiled a complete edition of the works of Claudio Monteverdi. Malipiero's relation with ancient Italian music was not simply aiming at a revival of antique forms within the framework of a "return to order", but an attempt to revive an approach to composition that would allow the composer to free himself from the constraints of the sonata form and of the over-exploited mechanisms of thematic development.

Igor Stravinsky's first foray into the style began in 1919/20 when he composed the ballet Pulcinella, using themes which he believed to be by Giovanni Battista Pergolesi (it later came out that many of them were not, though they were by contemporaries). American Composer Edward T. Cone describes the ballet "[Stravinsky] confronts the evoked historical manner at every point with his own version of contemporary language; the result is a complete reinterpretation and transformation of the earlier style". Later examples are the Octet for winds, the "Dumbarton Oaks" Concerto, the Concerto in D, the Symphony of Psalms, Symphony in C, and Symphony in Three Movements, as well as the opera-oratorio Oedipus Rex and the ballets Apollo and Orpheus, in which the neoclassicism took on an explicitly "classical Grecian" aura. Stravinsky's neoclassicism culminated in his opera The Rake's Progress, with a libretto by W. H. Auden. Stravinskian neoclassicism was a decisive influence on the French composers Darius Milhaud, Francis Poulenc, Arthur Honegger and Germaine Tailleferre, as well as on Bohuslav Martinů, who revived the Baroque concerto grosso form in his works. Pulcinella, as a subcategory of rearrangement of existing Baroque compositions, spawned a number of similar works, including Alfredo Casella's Scarlattiana (1927), Poulenc's Suite Française, Ottorino Respighi's Ancient Airs and Dances and Gli uccelli, and Richard Strauss's Dance Suite from Keyboard Pieces by François Couperin and the related Divertimento after Keyboard Pieces by Couperin, Op. 86 (1923 and 1943, respectively). Starting around 1926 Béla Bartók's music shows a marked increase in neoclassical traits, and a year or two later acknowledged Stravinsky's "revolutionary" accomplishment in creating novel music by reviving old musical elements while at the same time naming his colleague Zoltán Kodály as another Hungarian adherent of neoclassicism.

A German strain of neoclassicism was developed by Paul Hindemith, who produced chamber music, orchestral works, and operas in a heavily contrapuntal, chromatically inflected style, best exemplified by Mathis der Maler. Roman Vlad contrasts the "classicism" of Stravinsky, which consists in the external forms and patterns of his works, with the "classicality" of Busoni, which represents an internal disposition and attitude of the artist towards works. Busoni wrote in a letter to Paul Bekker, "By 'Young Classicalism' I mean the mastery, the sifting and the turning to account of all the gains of previous experiments and their inclusion in strong and beautiful forms".

Neoclassicism found a welcome audience in Europe and America, as the school of Nadia Boulanger promulgated ideas about music based on her understanding of Stravinsky's music. Boulanger taught and influenced over 600 musicians, including many notable composers, including Grażyna Bacewicz, Lennox Berkeley, Elliott Carter, Francis Chagrin, Aaron Copland, David Diamond, Irving Fine, Harold Shapero, Jean Françaix, Roy Harris, Igor Markevitch, Darius Milhaud, Astor Piazzolla, Walter Piston, Ned Rorem, and Virgil Thomson.