EXCLUSIVE: How Linda Perry and Sara Gilbert's 6-Month-Old Son Inspired Their Children's Album

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"The funny thing is, the first date we even went on, Linda was talking about, 'Oh, I've always wanted to make a children's album,'" Sara Gilbert tells ET.

Earlier this year, Gilbert's wife, Linda Perry, was inducted into the Songwriters Hall of Fame. Now, together with their family, the couple is embarking on a new professional journey. Deer Sounds, a children's album written and recorded by Perry, Gilbert, and their children, will be released on Sept. 18 and ET was first to sit down with the pair to chat about the project.

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"As soon as I got pregnant, I feel like the idea just started to get more real," Gilbert says, "and then when our son was born, it was just a no-brainer."

Now six months old, little Rhodes is credited as a songwriter on the album and the inspiration behind the whole project.

"I'd be holding him and singing songs, and then I was like, 'You know what, I'm gonna whip out my iPhone,' and I put it down and pushed record, and I was like, 'I think this might come in handy,'" says Perry. "I started playing it to [Sara] and the kids and they were like, 'That sounds like a children's album. You should write that' ... I asked Sara to help me on stuff and the kids jumped in, but Rhodes was the inspiration to all of it. I have to credit him because without him, it wouldn't have happened."

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Rhodes' heartbeat, from an ultrasound while Gilbert was pregnant, is featured on one of the album's tracks, as is a foot-stomping piano concerto.

"I put him on the piano and he just started, his little feet started going, and he starts making his noise and I was recording it, and we just started laughing," Perry recalls. "It was perfect. So we go, 'OK, well, that's obviously going on the album.'"

Deer Sounds features vocals from the entire family -- including Gilbert's son and daughter from a previous relationship, Levi and Sawyer, and the children of Perry's brother.

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"Basically it's me, and so I'm the leader of the band, and then we had a bunch of kids come in and sing different parts and made it like, a friends family kind of album," says Perry. "The whole concept that Sara and I really wanted to do was just, no matter what, we wanted to have fun doing this. That's it. That was the only intention."

Have fun, they did! But the pair is also hoping that both kids and their parents will connect to the material.

"The thing I love about the album is, it's not just for kids," says Gilbert. "Every parent's been in the car going, 'Oh my God, I can't hear this 'Car Goes Beep Beep' song one more time!' So, the album is really a family album that, some songs even sound a little bit more adult, that one could be a ballad for anybody. I think kids will love it, but it's got the sweetness that parents will understand about watching their kids grow up."

As for the album's title, Perry says Deer Sounds also represents the name of the family group – and she came up with the idea while brainstorming band names for one of her artists. "She didn't like it, and I'm like 'I'm taking it!'" Perry says. "It's got an alternative little flair, too, because with Deer Sounds, we could be anything, really."

"I love it," Gilbert chimes in. "It sounds sweet, but there's still a sophistication to it."

Tune in to ET next week for more from our sit-down, including an incredibly sweet mother-son serenade from Perry. (Seriously, the word "sweet" doesn’t do this moment justice. You won’t want to miss it!)

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