Yes, duct tape will work. It will in fact reduce vibrations.
It is not the best use of the product, nor is it efficient, but it will help to some degree, but it will also require TONS of it to make any difference, and will melt off in to a pile of go within a few weeks of summer.
When using the regular grey type of duct tape we all use for household projects, it is nearly impossible to use enough of it to get similar results that a real vibration damper will provide.
The thing about duct tape is that there are several types. Not all of them look exactlyk like the stuff we are all familiar with.
Tape, the is designed to go on a duct, is duct tape. Even the foil or mylar backed type is still duct tape.
There are 2 companies I know of that are currently a selling duct tape to consumers, and calling it a vibration damper.
many people on this exact forum have bought it, and used it, and continue to reccomend it.
So yes, duct tape, to some degree, will reduce vibrations.
Though the results might not be audible to the human ear, most anything you glue on to a resonating piece of sheet metal will to some degree help reduce vibrations. Even marshmellows..
ANT