Offstage brass and percussion
An offstage brass and percussion part is a sound effect used in classical music, which is created by having one or more trumpet players (also called an offstage trumpet call), horn players, or percussionists from a symphony orchestra or opera orchestra play a note, melody, or rhythm from behind the stage. This creates a distant, muted effect which composers use to suggest "celestial voices", melancholy, or nostalgia, or to create a haunting effect.
In Act III of Berlioz's opera Les Troyens, a group of offstage trumpets plays a distorted-sounding fanfare along with cornets to create an unusual dramatic effect. In Beethoven's overture for Leonore Overture and in Fidelio he used an offstage trumpet call.
In Respighi's The Pines of Rome, he uses an offstage trumpet for "Pines Near a Catacomb"; after the low strings play solemn chords, and the trombones play a simple, ancient-sounding Gregorian chant-style melody, an offstage trumpet introduces the piece's second theme. Richard Strauss used offstage trumpets during a battle scene in Ein Heldenleben ("A Hero's Life"). Aaron Copland's Quiet City used an offstage trumpet. Gustav Mahler's Symphony No. 2 uses an offstage brass ensemble of trumpets, French horns, and percussion. While the offstage trumpet's distant sound can create an emotional effect, critic Maurice Brown warned in 1971 that it can become an overused cliché.
Performance challenges 
Offstage music performed in the theater as an effect in a play is often less problematic than performing offstage music with an orchestra. In a theater context, the offstage sound effects are less likely to have to be synchronized exactly with other rhythms or pitches. For example, in some Shakespeare plays, the script calls for an offstage bugle call to indicate that enemy soldiers are in the distance. This cue does not have to be aligned with any other pitches or rhythms; it only needs to occur within the correct part of a scene, so a leeway of several seconds is acceptable.
Performing offstage music that has to be in sync with a larger ensemble on the stage involves potential problems with rhythm and pitch, because a difference of even a part of a second or a fraction of a semitone of pitch will be noticeable to the audience. If the conductor wants a truly muted and distant sound, the offstage player needs to be behind the stage or in an adjoining hall, not merely standing in the wings of the stage. If the offstage player is in an adjoining hallway or room behind the stage area, they may not be able to see the conductor or hear the orchestra. Even if they can hear the orchestra, their perception of the pitch and timing may be affected by the distance and refraction of the sound. If trumpet or French horn players attempt to tune their notes by ear to the orchestra pitch that they hear, their pitch may sound flat to the audience and conductor even if it is "correct" to the trumpeter or French hornists' ear, because a brass instrument's pitch varies over a long distance, and thus may sound flat in comparison to the orchestra.
To overcome these issues, conductors sometimes have an assistant who cues the offstage player, but this can result in miscues or time lags. These problems have led to a number of humorous anecdotes in the 19th and early 20th century, such as the case cited by Sir Malcolm Arnold, in which he jokes about a performance of Beethoven's Leonore Overture in which the offstage trumpet part was "conspicuous by its absence", because the backstage performer misunderstood the cue, and failed to play. Since the 1980s, both of these challenges have been surmounted with technology. To ensure that the offstage performer is in rhythm with the orchestra, a closed-circuit TV can be set up backstage to transmit video feed of the conductor's moving stick and hands. To ensure that the offstage performer is in pitch with the rest of the orchestra, the offstage performer can play while watching an electronic tuner which indicates whether they are sharp or flat.
List of pieces that call for offstage instruments 
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- Ludwig van Beethoven
- Leonore Overture No. 3 – 1 trumpet
- Hector Berlioz
- Havergal Brian
- Symphony No. 1 (The Gothic) – Four groups, each containing 2 horns, 2 trumpets, 2 trombones, 2 tubas and 1 set of timpani
- Benjamin Britten
- Serenade for Tenor, Horn and Strings – the solo horn in the Epilogue
- Gustav Mahler
- Krzysztof Penderecki
- Seven Gates of Jerusalem - 3 clarinets, 3 bassoons, contrabassoon, 4 horns, 3 trumpets, 4 trombones, 1 tuba
- Sergei Prokofiev
- Lieutenant Kijé Suite - 1 cornet
- Ottorino Respighi
- Dmitri Shostakovich
- Richard Strauss
- Pyotr Ilyich Tchaikovsky
- 1812 Overture – "Open" instrumentation consisting of "any extra brass instruments" available.
- Giuseppe Verdi
- Luisa Miller - 4 horns
- William Walton
- Belshazzar's Feast - 2 bands, each including 3 trumpets, 3 trombones and tuba
- Music and Gesture: New Perspectives on Theory and Contemporary Practice. By Anthony Gritten, Elaine King. Ashgate Publishing, Ltd., 2006 ISBN 0-7546-5298-X, ISBN 978-0-7546-5298-4. Page 98
- "Schubert's 'Fierrabras'". By Maurice J. E. Brown in The Musical Times, Vol. 112, No. 1538 (Apr., 1971), pp. 338–339 (article consists of 2 pages). Published by: Musical Times Publications Ltd.
- Anatomy of the Orchestra. By Norman Del Mar. University of California Press, 1982 ISBN 0-520-05062-2, ISBN 978-0-520-05062-4. Page 322
- The Life and Music of Sir Malcolm Arnold: The Brilliant and the Dark. By Paul R. W. Jackson. Ashgate Publishing, Ltd., 2003 ISBN 1-85928-381-0, ISBN 978-1-85928-381-3. Page 117