Adam Aijala says Yonder Mountain String Band has never been a group to plot out its career — or just about anything the group does. To hear him tell it, there was no strategy to the path that has carried the group from do-it-yourself upstarts that self-released its early albums to a place where it is now one of the leading acts on the bluegrass/jam band scene. These guys couldn’t be calculated if they were math majors.

“That’s kind of the way we do it,” guitarist/singer Aijala said in a recent phone interview. “It seems like from the very beginning, even our shows are like that. We don’t play the same set every night. We’re always kind of winging it in general. I’d like in the business sense to maybe not wing it as much, but as far as the artistic side, I like that element of it.”

So perhaps it’s not surprising that when Yonder Mountain String Band’s future was thrown into question in April of 2014 — after mandolin player Jeff Austin left the group, — there was no clear plan for how to move forward.

Now, two-plus years later, Yonder Mountain has come out of that time of uncertainty smelling like a rose. Two new members have joined — mandolin player Jacob Jolliff and violinist Allie Kral — and the group is moving full speed ahead.

“The way it all played out was not planned at all. We didn’t know what was going to happen,” Aijala said, when asked about confronting the Austin-less future. “We had some people in mind other than the people we’re playing with. And the way it worked out, I think, I really hope they (Jolliff and Kral) stick around. I love playing with them.

“They’re having a blast, too. I always check in to make sure they’re still cool. They’re loving it. Maybe this will be something that goes on for awhile.”

Yonder Mountain String Band brings their tour Sunday to Blue Moose Tap House in Iowa City.

Kral, in a case of excellent timing, crossed paths with Yonder Mountain just before the split with Austin occurred.

“I’d met her a handful of times,” Aijala said. “She sat in with us a couple of times over the years. And really, she sat in with us on that last tour with Jeff in April (2014) for like three different shows.

She came to some different shows. She lives in Portland and it was when we were up in the Northwest. And we had a blast. And hanging out with her, I was like ‘This chick’s cool.’”

Jolliff, however, wasn’t someone who’d had met or jammed with the group. Instead, his name came up via Yonder Mountain’s former manager, DJ McLaughlin, who knew Jolliff was looking for a gig.

“He (McLaughlin) is like you should really call him,” Aijala recalled.

“He’s like ‘You know I know you, Adam. He’s a lot younger than you guys, but I know you’ll get along with him. He’s a standup dude. He comes from a solid background, a great musician. You should call him.’... And next thing you know, he (Jolliff) is on a plane out here and we’re in the studio working on the new record.”

That excellent latest record was released in June 2015. It’s called “Black Sheep,” and its arrival may have come as a pleasant surprise to many Yonder Mountain fans.

That’s because prior to Austin’s departure, it looked like album making would not be as much of a priority for the group.

The three band members — Aijala, banjo player Dave Johnston, and bassist Ben Kaufmann — had seen their time for writing and recording diminish as they got older and family obligations joined Yonder Mountain’s extensive touring schedule in limiting the time left for studio work.

The release in early 2014 of the four-song EP, “EP 13,” ended a four-year gap that had followed the release of the group’s previous album, 2009’s “The Show.” Before Austin left, the group members were thinking that making EPs, which take less time to write and record, might be the best way to get new music to fans.

Then Austin’s departure changed that line of thought and put the idea of doing “Black Sheep” (which is a full-length album, by the way) on the front burner.

“In light of Jeff’s departure, we thought it was important to make it a priority, to have something new to deliver, so people could see a representation of the new sound,” Aijala said.

Fans will still recognize “Black Sheep” as the work of Yonder Mountain, even without Austin, who along with Johnston, Aijala and Kaufmann, formed the group in 1998 in Nederland, Colorado. In fact, because “Black Sheep” is a largely acoustic album without drums, it in some ways is more similar to Yonder Mountain’s first couple of albums – which introduced the group’s tuneful and energetic blend of bluegrass-rooted music and rock improvisation — than the group’s 2006 self-titled album and “The Show.”

The latter two albums were produced by Tom Rothrock (who is known for his work with rock acts like Beck, the Foo Fighters and Elliott Smith) and added a notable instrument to Yonder Mountain’s music — drums.

“I think that this album (“Black Sheep”) is more akin to ‘Elevation’ and ‘Town By Town,’” Aijala said, referring to the band’s first two albums.  “But it’s also the band that’s been around for 17 years, too, so it’s evolved as well.

“And that’s not to diminish the records we did with Tom (Rothrock),” the guitarist said. “I think those records were great and they were really fun to do, and he really helped us get to a point where our only limitations in music are our musical abilities. It’s not the style or what we do with it, or what instruments we play or any of that.”

Aijala doesn’t hesitate to say Yonder Mountain is also a different band live without Austin, who was a charismatic performer and a focal point on stage. But he likes what Jolliff and Kral bring to the live show.

“I think it’s a huge difference,” the guitarist said. “You know, it’s one of those things where it’s different, but it’s still good. It’s different and for me, I’m loving it. I feel like the Yonder energy is still there, and this is not a dig on Jeff at all, but he tended to take us to a darker place sometimes. We don’t really do that as much (now). That’s just a fact. I’m not saying that in a negative way at all. I think that  (darker edge) was a good quality as well. But I can’t be who I’m not. I am who I am.

“Ben’s picked up a lot of the interaction with the crowd. I think he’s doing a really good job,” Aijala said. “Allie’s stage presence is awesome. People just love her. There are like women and men screaming ‘Allie, Allie,’ like every show. It’s awesome. And Jake’s just a demon. People look just look at him while he’s soloing, and putting their arm’s up the air like ‘What the hell? This dude’s out of control. He’s so good.’ So it’s a different dynamic completely. It feels more, I don’t know what the (word is), there’s more camaraderie.

Even though we were super tight with Jeff, maybe it’s because these dudes are stepping into something new, and so therefore they’re paying a lot of attention. But I feel on and off stage, I feel really synced.”

GET OUT!

Who: Yonder Mountain String Band with special guests The Railsplitters
When: 8 p.m. Sunday, Jan. 22. Doors open at 7 p.m.
Where: The Blue Moose Tap House, 211 Iowa Ave., Iowa City
Tickets: $25, $30