Professional speller, punctuator and grammarian. Wow that's a challenge.

Certainly a sentence can begin with a conjunction, modern English usage allows that. Doing it twice in one short paragraph looks as if it is a trap that has been set for the unwary pedant.

There is a case to be made for commas after brass bander and at the end of the clause in parentheses. I would definitely argue for a comma after euphonium, and that the second exclamation mark is superfluous.

What do you mean put this white coat on?

Ok doctor I am coming..........................................

Sorry about the thread drift Ralphie......