Jessica Simpson and Nick Lachey of 98 Degrees will take their well-documented musical affection for each other to the public next week, as the couple is set to perform its "Where You Are" duet at the New York City premiere of "Here On Earth."

On March 23, Simpson and Lachey are scheduled to sing their joint hit prior to the screening of "Here On Earth" at Manhattan's Ziegfield Theater for the film's cast, including star Leelee Sobieski.

"Where You Are" is the lead song on the "Here On Earth" soundtrack, which arrived in stores this week. "Here On Earth," a film about a boy who falls in love with a girl with a terminal illness, will be released to theaters nationwide on March 24.

Simpson and Lachey have been romantically linked since she opened for 98 Degrees in 1999, and she publicly admitted to their relationship during an MTV interview last October (see "Jessica Simpson Chats About Her Love Match With 98 Degrees' Nick").

Simpson's next performance will be in the sunnier climes of Florida, as she's scheduled to play a series of weekend shows at Disney World in Lake Buena Vista, beginning on April 28 and 29 and continuing through May 12.