Watch The Judds Sing Together for the First Time in Five Years Ahead of Vegas Show

Wynonna Judd and her mom Naomi Judd are returning to Las Vegas and only ET was invited to their rehearsal.

"Thank you, ET, for being here, because this is our first time singing together in five years," Wynonna told us.

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The Judds' first No. 1 song, 1984's "Mama He's Crazy," launched a string of hits that currently totals 14. They've earned five GRAMMYs and sold more than 20 million albums, but they're not done yet. The ladies are preparing for a nine-show residency at The Venetian in October.

We caught up with Naomi, 69, and Wynonna, 51, at their vocal coach's house where they were practicing.

"The voice is a muscle," said Wynonna, who came to join her mom already in the rehearsal process. "I've flown in today to wrap it all up, and we fly out Saturday."

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You can expect the women to belt out their biggest hits for the show called Girls Night Out.

"We know that a whole lot of our fans are coming -- like billions of them -- because they've been asking us to do this," Naomi said. "And I've been doing rhinestones. My little fingers are down to nubs right now."