The udjudg was a special musical instrument played by the Zybahhod Yenyoni. They were uniquely suited to play it with their "Y"-shaped naso-facial openings.
Behind the scenes[]
The udjudg was created by Jennifer Kay, a Star Wars fan, for the backstory of her Zybahhod Yenyoni entry in the Design An Alien contest held in the Star Wars Galaxy Magazines.