Following the sudden and tragic passing of 'Glee' star Cory Monteith on July 13, his co-star and friend Matthew Morrison took to the stage with a song dedication as part of his one-man show, 'Up Close and Personal with Matthew Morrison.'

"We lost a great young man too soon," a source reports Morrison telling the crowd. "You came out to see a show, I came out to do one, so let's honor Cory with this performance."

Calling Cory as a "beautiful person," Matthew then performed 'What I Did For Love' from the musical 'A Chorus Line,' obviously struggling with his emotions.

"It was difficult for him to get up to perform, but he did not want to disappoint anyone," the insider explained. Yet a different source added that "Matt is beside himself" over Cory's passing.

As for the song choice itself, while a strange pick on the surface, has poignant lyrics -- and it was performed by Monteith's real-life girlfriend Lea Michele on 'Glee.' You can listen to that below.