Every Christmas, Halloween and Valentine's Day since the mid-1960s, children and adults alike have wondered who, exactly, is this unseen, enigmatic teacher that guides Charlie Brown, Linus, Pigpen and the gang through their never-ending elementary school years?
Laying aside, for the moment, the grafting of Charlie Brown's teacher onto your boss, parents, parole officer and so forth when you didn't feel like listening to hir, you may notice that the teacher has a distinctly musical voice. Despite the endless intonations of "mwah mwah mwah mwah," the invisible educator is actually speaking, if you listen closely enough and use your imagination.
For those of you that seem to remember in a long-lost, deep subconscious sort of way, of the teacher saying "Charlie Brown, you're late again," you may be interested to know that you were not experiencing an aural hallucination.
"Composer John Scott Trotter directed his trombonist to 'enunciate' the teacher's dialog as though it were a trombone riff. Trotter did a great job... he would read the teacher's line, e.g., 'Linus, where's your homework?' then direct the trombonist to repeat Trotter's inflection through his instrument."
So there you have it. Charlie Brown may have been a putz under most circumstances, but at least he could speak brass.
Source: quotation from http://davespicks.com/pictures/vacation1999/f/21.html