It's not too hard to sing well, if you've got a built-in echo chamber sitting on your face.
LOL!
Y'know, it's sad to contemplate what a career Streisand threw away.
In her youth, she really had a talent for comedy. "The Owl and the Pussycat" and "What's Up, Doc?" are great showcases for her.
Then she decided she'd rather do "serious" movies, and the result was "Yentl." Ugh. She could have been one of the 20th century's most noted comediennes, and instead she's a glorified lounge singer whose appeal is limited to New York and Florida.