Lily & Madeleine on finding their "third voice"

Lily & Madeleine talk "Canterbury Girls"

Sisters Lily and Madeleine Jurkiewicz got their start singing cover songs and posting them online. When their videos caught the interest of a music producer, their recording and performing career was borne. 

"Did you have to negotiate this all at the beginning? Or did it just evolve?" "CBS This Morning: Saturday" co-host Anthony Mason asked the duo in a recent interview at Brooklyn's Rough Trade Records.

"It just evolved. Lily's more of an alto in her voice and I'm more of a soprano, so we've always just kind of had an agreement. And that's how we go about it," Madeleine said.

The New York Times called their sound "deep and seamless and relaxed." But when they separate, Lily said, they sound completely different. 

"I feel like we lock into like a third voice that's like not there," Lily said. 

Their new album, "Canterbury Girls," is named after a park in Indianapolis where they grew up. The sisters first sang professionally there as teenagers and recorded their first songs while still in high school. Their career got a boost when they performed with another Indiana native, John Mellencamp. But they're not really sure how it all began.

"I think it's because of our mom. Because she was so musical and she would sing with us. And she also tried to teach us French when we were little and we'd sing little nursery rhymes. She is the best," Madeleine said. "It did come naturally and that's why I think it's been so easy to progress."

Being sisters can come with its problem, too. It's something they said they've been thinking about a lot recently.

"It's just that obviously I love doing this with her, but I don't have an individual identity at this point. And doing it with her is the only thing that defines me, which I love and I would never stop if I can help it. But also, like, my personal life, like what's going on there. I don't really know," Lily said.

Lily, who's now 21 and Madeleine, who's 23, recently moved together to New York City, but the sisters are on the road again, off on their biggest headlining tour yet — and they're pretty much doing it all themselves.

"We're driving ourselves. We're tour managing everything, advancing the shows," Madeleine said. "Our music it touches them and I had no idea … People have these stories and it really makes you feel like what you're doing is worthwhile."