Tenor trombone, silver-plated slide: America, end of 19th century, brass dragon-head bell: France, ca. 1820/30 (Musikinstrumentenmuseum Schloss Kremsegg, Austria, Streitwieser collection)
The trombone symbolizes the hereafter, the supernatural, hell and the underworld. Its powerful sound is supposed to conjure up images of the terror and unknown dimensions of these realms of darkness. Particularly in requiems (Mozart, Berlioz, …) the trombone section, often large, is assigned the role of evoking the audience’s fear of crossing over to the hereafter in the Dies irae and Tuba mirum. The symbolism is therefore religious, as it has been in opera, too, since Monteverdi (Weber's "Freischütz").
The increase in the number of playing techniques in the 20th century, partly inspired by jazz, enabled the trombone to take on entirely new roles in very “secular” contexts. New effects such as glissando, flutter tonguing and the use of various different mutes endowed the instrument with possibilities for expression ranging from solo narration to parody and burlesque. It is this aspect of the trombone that is being developed further in more modern works.