Musicians in bands will sometimes talk about the immediate connection they felt when they first played with their bandmates. In the case of Boulder, Colorado, roots trio The Sweet Lillies, the connection was so strong, it led one member to move to another region of the country.

Upright bassist/mandolinist Julie Gussaroff and violist/percussionist Becca Bisque started the group in 2013, and had been playing together for about two years when vocalist/percussionist Melly Frances sat in with the band at a show in a little mountain town in Colorado. Singer-songwriter Frances was on tour at the time, and after playing a full set with The Sweet Lillies, she was on her way back home to California.

Not long after, Gussaroff needed a vocalist for some big shows coming up and called Frances.

“I called her up, and I said, ‘Hey, do you want to move to Colorado and join the band?’” Gussaroff said from Bigfork, Montana — the trio was getting ready for a day of skiing during a break on its West Coast tour. “And that’s what she did. She dropped everything, and she came straight to Colorado.”

The newly minted trio played its first show at the Fox Theatre in Boulder in December 2015. Two days later, the trio wrote its first song together.

“We all felt it,” Gussaroff said. “When that kind of musical connection happens — even this first tour with (touring guitarist) Jack Cloonan, it’s the same thing — the bar raises (and) the excitement grows. It’s like love at first sight or something. You fall in love with each other musically.”

The purest version of that musical chemistry will be on display at the trio’s show Tuesday night at Volcanic Theatre Pub, since the band’s usual touring musicians Cloonan and banjoist Chris Elliott won’t be at this date. (The band will probably hit the ski slopes when it’s in town, naturally.) It will actually be the band’s second show at the venue — in 2014, the early version of the group, sans Frances, performed there — but given the evolution that’s occurred since then, it might as well be the first.

Perhaps most noticeably, the group’s three-part harmony singing has become a key component of its bluegrass- and soul-inflected sound, as exemplified on its 2016, self-titled debut album. The trio works with vocalist Kim Dawson, of Brooklyn funk/Afrobeat band Pimps of Joytime and a friend of Gussaroff’s (the two taught at the same music school for a time), to fine-tune its vocals.

“What (Dawson) says about our voices is, she’s like, ‘There’s two types of great harmony vocals. … They can either be because you’re related and you sound a lot alike, or they can be because the voices are different’ — the way that our voices are all different, but then, they come together in this really powerful way,” Gussaroff said. “Becca and I always envisioned a three-part, female harmony-driven sound.”

Pimps of Joytime may be an unexpected connection for an acoustic roots band. The rest of the trio’s influences are equally varied, ranging from key players on the newgrass scene such as Fruition, Leftover Salmon and Yonder Mountain String Band, to folk rockers Brandi Carlile and Front Country, to indie rockers such as My Morning Jacket.

In turn, constant touring has ingratiated the band with the modern string-band movement. The trio has shared stages with at least one of its influences — guitarist Vince Herman of Leftover Salmon — as well as Kyle Hollingsworth of The String Cheese Incident and Andy Hall of The Infamous String Dusters, according to the band’s website. Herman also co-produced the trio’s upcoming second studio album with Andrew Gragg Lunsford, who helmed the group’s first album.

“I actually was having a conversation with (Leftover Salmon co-founder) Drew Emmitt about this. … We were at Hangtown (Festival, Placerville, California), and I was talking to Drew Emmitt about, ‘Do you feel a sense of having created a genre a little bit?’” Gussaroff said. “And I was just asking him about it because in my mind, someone had to set the stage for this, and those are the kind of people that did it. And people like traditional players were like, ‘What are you doing?’ when they first heard it, and now, it’s like the best thing ever, biggest thing ever.”