Overture of Pirates & Iolanthe = P I
Begin old fashioned = BROCH (an early form of BROACH)
PIBROCH = piped music
Extra word chamber
The only really thematic submission is the submission of a blank grid
There were plenty of elements in this puzzle to keep us amused
The G & S Red Herring
The S & G song chiming with the "classical" piece
The musically themed clues to cold solve & extra words to identify
The Carte Blanche jigsaw to complete and identification of the theme
The ordering of the extra words to get the two messages
The cursing and the eventual grudging realisation
Good joke, Pilcrow. Restful New Year for Mr. Green