Mutes are used to create different sounds on the horn. Straight mutes create a more distant, far-away sound.  Stop mutes create a brassier, edgier sound.

Composers use different words to indicate whether they would like a straight or stop mute used.  Con sord., short for con sordino, is Italian for “with mute” and indicates a straight mute. 

The ” + ” sign or the markings “stopped, gestopf, or bouché” in music indicate a stop mute.

When you see senza sordino, this means “without mute.”

Frequent travelers may also have a practice mute which will muffle the sound coming from their instrument so they can practice in hotel rooms or other situations where loud noises would disrupt others. Use these sparingly, as they create a resistance that is radically different from open playing.