It has been confirmed that Morrison, who plays Glee club teacher Will Schuester on the series, will perform the ballad 'Still Got Tonight' on the upcoming New York-themed episode.
The single, from Morrison's self-titled debut album, was co-written by former American Idol winner Kris Allen.
"It was going to be just a big dance piece with me doing this big dance number," Morrison explained to The Hollywood Reporter. "But they said, 'We want you to sing it and make it a big moment'."
The actor explained that series creator Ryan Murphy was keen to use 'Still Got Tonight' in the episode, and convinced Fox chairman Dana Walden that singing an original song would be in keeping with the character.
"We worked really hard to make it feel organic to the show," Murphy said, regarding the song's inclusion.
The season two finale of Glee is scheduled to air in the US on May 24.