With horn players, what we put in the bell is very important. It starts at the very beginning with how to hold the instrument. The right hand position can make or break things like tuning, tone quality, projection, how easily the instrument plays, and even the range.
While muted passages become more common as players advance, the need for a mute in band or orchestra can happen after only a couple years. As with the position of the hand, the mute choice makes all the difference in how the horn plays.