Glee star Matthew Morrison debuted his first single off his upcoming album -- a duet with Elton John!

The song, which sneak-peeked this morning On Air With Ryan Seacrest is a mash-up of Elton’s hits “Mona Lisa And Mad Hatters.”

“It’s … really fantastic,” Elton John said of the single. “He sings great on it.”

Would Mr. Shue approve?