The trombone is a musical instrument in the brass family and use a telescopic slide mechanism that varies the length of the instrument to change its pitch. Some trombones also have a valve attachment as a means of lowering the pitch of the instrument. The origin of the name ‘trombone’ is the Italian ‘tromba’ (trumpet) and ‘one’ (a suffix meaning "large"), so the name really means "large trumpet".

The instruments most frequently encountered in the orchestra are the tenor trombone and bass trombone. The tenor trombone, is a non-transposing instrument pitched in B♭, an octave below the B♭ trumpet and an octave above the pedal B♭ tuba. Trombone music is typically written in concert pitch in either bass or tenor clef, although exceptions do occur, notably in British brass band or concert band music where tenor trombone is presented as a B♭ transposing instrument, written in treble clef.
The composer typically credited with the trombone's introduction into the symphony orchestra  was Beethoven, who used it in the last movement of his Symphony No. 5 in C minor (1808). He also used trombones in his Pastoral Symphony No. 6 in F major  and  his Choral Symphony No. 9.

Many composers were directly influenced by Beethoven's use of trombones, and they became fully integrated in the orchestra by the 1840s. Early to mid 19th-century composers such as Schubert, Schumann, Mendelssohn, Wagner, Berlioz, Rossini, Verdi, Liszt and Gounod all included trombones in their operas, symphonies and other orchestral works.
The Alderley Edge Symphony Orchestra