Black Tie Guide visitors occasionally ask me if it’s okay to wear suspenders with cummerbunds. My first thought is “why don’t these people bother reading the Guide before writing?” My second thought is “why do so many people assume these two articles are mutually exclusive?”
I suspect that a general unfamiliarity with the cummerbund leads many to equate it with a belt because of the manner in which it is worn. In that regard, it would indeed seem redundant to use two types of trouser holders at once. It is also possible that most people today assume that braces are no more than a decorative novelty.
Therefore, I typically respond to this question by explaining the role of each item. Suspenders are a practical accessory designed to hold the trousers in place like a belt while the cummerbund is an aesthetic accessory intended to conceal the trouser waistband and the undecorated shirtwaist like a waistcoat.
I will also often use the opportunity to remind the writer that there is no need to worry about the two articles matching because, unlike shoelaces or belts, braces are never meant to see the light of day (or night.)