Keith Urban is loving getting the chance to pass on his musical know-how as the Mega Mentor on season 25 of The Voice — but it seems like guitar lessons at home aren’t going quite as smoothly!

After previously expressing a desire to teach wife Nicole Kidman how to play the guitar, Urban admitted to ET’s Cassie DiLaura that it’s been slow going — and not just because of the A-list couple’s jam-packed schedules.

“[It’s going] not so good,” Urban shared with a laugh. “I gotta find a great left-handed guitar. Obviously, that’s the first step.”

In the meantime, Urban debuts on The Voice season 25 on Monday as the Knockout Rounds kick off — returning for the first time since he served as a mentor for Blake Shelton’s team back in season 15. 

“It’s actually fun, yeah. The teams are strong and I love this part of the journey,” he shared of returning to the reality competition. “I love being around artists. I just- I’m at home around artists.”

This time around, Urban helps out with all four of the teams — joining coaches Reba McEntire, John Legend, Chance the Rapper and first-timers Dan + Shay as they coach their teams in the Knockouts.

“They’re all pro artists. So there’s a good creative flow,” he said of working with each team and contestant’s different styles. “They’ve all got strengths in different areas — the way they put their teams together, I can see what they’ve done.”

As for working with the up-and-coming talent, Urban said that his background in producing helps a lot.

“I think you’re trying to find a good key and a good tempo and a good arrangement of a song, and just help them be their best, really,” he explained.

Plus, as it turns out, the country superstar has reality singing experience of his own. A teenage Urban made an appearance on a TV talent show called New Faces in his home country of Australia all the way back in 1983 — singing Air Supply’s “All Out of Love” — and of course, ET had to show him the nostalgically hilarious throwback.

“Look at those teeth! Come on now,” he teased. “I literally look like I’ve raided ABBA’s wardrobe.”

Urban joked that what he first remembers about the New Faces experience was “my parents lying about my age.”

“I think I was 14 and I said I was 16, because you had to be 16 minimum to get on the show,” he recalled with a laugh. “Go Mom and Dad.”

But he also remembered the nerves that came with performing in front of a crowd and receiving public critiques — something he’s kept in mind while mentoring The Voice hopefuls.

“Every bit of it is hard — being on that stage, singing in front of all of us, like, that’s hard. It’s nerve-racking,” he noted. “They’re probably singing a song they’ve never sung before. They’re standing in front of us. It’s just, it’s hard.”

Some of the best advice that the four-time GRAMMY winner has received? “Stay curious.”

“Curiosity kind of cancels out everything else,” he noted. “You can’t be jaded. You can’t be arrogant. You can’t be cynical. You can’t be lazy. And you can’t be any of those things if you’re curious and just stay in a place of interest and curiosity and hunger.”

Alternately, Urban said, it’s important to know “which advice to take and which to discard.”

“We all need advice, all of us, all the time,” he shared of his personal philosophy. “[But] it’s not all meant for us. I always remind people, ‘This is just my feeling about it.'”

“[Someone] might say, ‘I hear you. I disagree with everything you said. I’m gonna do none of what you told me to do.’ And then they end up becoming this incredibly unique artist because they knew who they were,” he continued. “So I think it’s also knowing what advice to not take.”

The Voice airs Mondays at 8 p.m. PT/ET on NBC.

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