In music, the inclusion of musical materials in a composition that allude to other compositions or musics. Folk songs, contrapuntal elaborations on a given CANTUS FIRMUS, and the doom-laden chant DIES IRAE have been a favorite resource for centuries.

Some famous examples of musical quotation include:

RICHARD STRAUSS inserted the theme of the funeral march from LUDWIG VAN BEETHOVEN'S Eroica Symphony in the score of his METAMORPHOSEN, a dirge on the death of Germany, written during the last weeks of World War II.

ALBAN BERG quoted JOHANN SEBASTIAN BACH'S chorale Es ist genug at the conclusion of his Violin Concerto as a memorial for Manon Gropius, the young daughter of GUSTAV MAHLER'S widow by another marriage.

An extraordinary assembly of assorted thematic memos, memories, and mementos is found in Sinfonia by LUCIANO BERIO, in which he quotes metamorphosed fragments from works of Mahler, CLAUDE DEBUSSY, MAURICE RAVEL, and others.

JOHN CAGE'S EUROPERAS, comprised of nothing but collaged fragments from extant operas across several centuries, epitomizes the practice.

The situation is different, of course, when a quotation of a famous song is deliberately made for purposes of characterization or historical reference, as for instance the MARSEILLAISE in PIOTR ILYICH TCHAIKOVSKY'S 1812 OVERTURE and in UMBERTO GIORDANO'S ANDREA CHENIER, or THE STAR-SPANGLED BANNER in GIACOMO PUCCINI's MADAMA BUTTERFLY. Cage's works may also be construed in this light.