He could have correctly dispensed with the cummerbund had he worn a black waistcoat.
From the washingtonpost.com
His cummerbund hit the floor just as he stopped before news photographers.
From the bostonherald.com
Victorya Hong's line includes sleeveless designs cinched with a cummerbund-style belt.
From the washingtonpost.com
The ivory satin bodice had a black lace overlay with a black cummerbund.
From the al.com
Tuxedos are designed to be worn open with the vest or cummerbund showing.
From the al.com
A leisure suit with a cummerbund and a clean bowling shirt can create a tacky appearance.
From the al.com
Blue and various shades of red or green are the most common colours for the cummerbund.
From the en.wikipedia.org
A cummerbund is never worn with a double breasted jacket, and a waistcoat now very rarely.
From the en.wikipedia.org
This is a bit like wearing a clown suit with a cummerbund, unfortunately.
From the npr.org
More examples
A broad pleated sash worn as formal dress with a tuxedo
A cummerbund is a broad waist sash, usually pleated, which is often worn with single-breasted dinner jackets (or tuxedos). The cummerbund was first adopted by British military officers in colonial India as an alternative to a waistcoat, and later spread to civilian use. ...
An overlapping waistband with Velcro used to secure a Buoyancy Compensator snugly around the diver's waist.
Wide cloth band worn as a waist sash. Part of traditional male dress in India, Iran and South America, later adopted by men as an alternative to a waistcoat and by women as a belt. examples
Folded or pleated silk or rayon waistband worn with dinner jacket.
Formal, pleated, adjustable waist sash, worn with pleats up.
A wide sash worn at the waist - usually with horizontal pleats worn by men with a tuxedo for evening wear (6)
A pleated sash wrapped around the waist, either patterned or plain.
A sash worn as a belt, it covers the pant button, top of the zipper, and where the shirt tucks into the pants. Can also help hold in the abdomen. Pleats face up, bow tie should match.