Melissa McCarthy Keeps Barbra Streisand Laughing Behind the Scenes of Their 'Encore' Recording Session

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Barbra Streisand told ET all about how her collaboration with Melissa McCarthy came together for Babs' duets album, Encore: Movie Partners Sing Broadway.

"She was delightful!" Streisand gushed. "Just so funny."

WATCH: Barbra Streisand Sings 'At the Ballet' With Anne Hathaway and Daisy Ridley

Of all the celebs Streisand called on to join her on the album, McCarthy might have been the most starstruck

"I heard you had a Starbucks in your house," McCarthy joked in a clip. "And all the employees have to wear cashmere."

While McCarthy shines under Streisand's direction, the Ghostbusters star was a bit out of her element in the recording booth.

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"She does at times sing fantastic," Streisand said. "And then at other times ... My point is, you know, she is not a professional singer."

Encore also features collaborations with Seth MacFarlane, James Brolin, Alec Baldwin, Antonio Banderas, Hugh Jackman, Jamie Foxx, Patrick Wilson, Chris Pine, Daisy Ridley and Anne Hathaway.