In bands consisting of all or mostly wind instruments (i.e. jazz or wind orchestras), the most lowly and usually worst player in a section of trumpets. The Mute Boy has one job: get the mutes, no questions asked.
The title is assigned at the beginning of a school year or season beginning, by the section leader, and lasts for the duration of said season or year.
-"Where are the mutes?"
-"I'm not sure, where's the mute boy?"
-"Oh look, there he is- STFU AND GET THE MUTES"