Less than 24 hours after news broke that "Glee" star Cory Monteith was found dead in his Vancouver hotel room, his costar Matthew Morrison held a concert in NYC ... paying tribute to his late friend.

The actor performed at 54 Below in New York on Sunday, starting the show by speaking about Cory and dedicating a song to him.

"We lost a great young man too soon," Matthew told the crowd, according to Us Weekly. "You came out to see a show, I came out to do one, so let's honor Cory with this performance."

Morrison then performed "What I Did for Love" from "The Chorus Line," a song Lea Michele once performed on the show.

According to the magazine's source, Morrison was "very emotional on stage" and "it was difficult for him to perform, but he did not want to disappoint anyone."

We can only imagine how tough it was to go on at a time like that.

So far, a bunch of "Glee" costars have spoken out about Cory's death on Twitter -- with guest stars like Kristin Chenoweth, Ricky Martin, Neil Patrick Harris and Cheyenne Jackson all tweeting about the young star.

Click here to see what they and more celebrity friends and fans had to say.

And to see some of his most memorable performances on "Glee," click here.

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