Anyone who likes musicals should experience the very charming The Drowsy Chaperone if he or she gets a chance to see it. The book by Bob Martin and Don McKellar salutes American musicals of the Jazz Age and, although it starts to sag after a while, is effectively mirthful and casually smart. The music–by Lisa Lambert and Greg Morrison–seldom disappoints. True, “Cold Feets” doesn’t cut it, but such songs as “Show Off” and “Love is Always Lovely in the End” are pleasant and exciting items. As long as the singing and dancing are acceptable (they usually were in the local production I saw), it’s a heck of a show.