Analysis of information sources in references of the Wikipedia article "Mute (music)" in English language version.
In many instruments of this family... there is one particular tone elicited by the bow which sounds quite different from the rest, but the wolf tone is most well known... in the cello.
CHICAGO, July 22.—Patrick (Paddy) Harmon, promoter and first president of the Chicago Stadium... died today
1949: ... patent granted for the Heifetz Mute (developed with Henryk Kaston)
Sure, you could use a mute, but that will alter the tone—at least occasionally you want to hear yourself playing at full throttle in order to master performance-level technique.
Since the most commonly used brass instrument mute is the straight mute...