How one often spells the word "embouchure" (because "embouchure" sounds like it should be spelled "ombusher") -- the use of the facial muscles and shaping of the lips when playing a wind instrument like a tuba or trombone.
You're putting too much pressure on the mouthpiece. Relax the ombusher. Don't use any muscles you don't need.
by Telephony January 04, 2011