In music, the act of playing more than one instrument for a recording or during a performance. Literally, "to double", or "doubling".

Common doublings are:

  • A flautist is almost always capable of playing the piccolo. The bass flute, pitched a full octave lower than the flute, should also not be a problem. The alto flute, or flute in G, is a transposing instrument but likewise should not be difficult. the difficulty in writing for bass or alto flure is in actually aquiring the instruments.
  • Clarinet players should be able to play bass clarinet and tenor saxophone as all of these instruments are in Bb. The technique does vary from instrument to instrument but if you are writing doublings, professionals should be playing your piece in the first place. The contrabass and contra-alto clarinet, while fearsome to lug around, should also be in the repertoire of a respectable clarinetist.
  • Saxophonists should be able to play any saxophone. The possible exception here is asking a soprano specialist to throw down on a bass saxophone, since the size of the instrument and thus the mouthpiece varies so much. Embouchure is a cruel bitch mistress, and no aspiring composer should forget that.
  • Oboes can usually double on an english horn (pitched in F) and more rarely, the oboe d'amore and the bass oboe. The oboe d'amoure will prove more difficult considering that it's transposition (a minor third up, in the key of A) is kind of odd, although not unheard of. This same theory belies the ability of the bassoon family, in that a bassoon player can almost always play a contrabassoon.
  • Horn players are almost always protective of their embouchure and as such are loathe to play other brass instruments.
  • Trumpet players can usually play cornets and alto trumpets, or as Rimsky-Korsakov called them, the "little trumpets in D".
  • Trombone players are usually more than happy play bass trombone so long as the instrument in question features a trigger system similar to their own horn.
  • Tuba, euphonium, and baritone players are usually interchangable. The euphonium and baritone are relatively new instruments but all are in C and feature common fingering systems.
In short, you shouldn't expect anyone but an extreme specialist to be able to play a tenor sax for 18 measures and then pick up a french horn. I'm sure people like this exist but don't write around the assumption.