Department of Eagles has achieved some pretty impressive feats for a non-band band: Its album "In Ear Park" (4AD) has impacted a good number of Billboard's charts, including a No. 3 bow on Top Heatsee

Speaking from a remote house near Cape Cod, Daniel Rossen spends a few minutes explaining why his musical endeavors in Department of Eagles is different from his primary band, Grizzly Bear.

"[Department of Eagles] is not a band. It's more of a music project. We're a songwriting team. It really turned into more of a project than it was gonna be," 26-year-old Rossen tells Billboard.com.

Whatever it is, Department of Eagles has achieved some pretty impressive feats for a non-band band: Its album "In Ear Park" (4AD) has impacted a good number of Billboard's charts, including a No. 3 bow on Top Heatseekers and a No. 166 peak on The Billboard 200.

Department of Eagles formed during Rossen's freshman year at NYU, when chance put him and co-songwriter Fred Nicolaus together as dorm roommates. Down the hall, too, was Chris Taylor, who also joined Department of Eagles and, later, Grizzly Bear. In fact, three of the four main contributors to these Eagles are also in the mammalian crew: Rossen, Taylor and drummer Chris Bear.

"We really didn't know what to expect, if Grizzly Bear fans would be interested in this," Rossen says. "And the last thing we wanted was to make Grizzly Bear fans think that we were splitting up because of this."

Obviously, sales for the album have been boosted by Grizzly's critical reputation but, stylistically, "In Ear Park" (produced and engineered by Taylor) departs from Grizzly Bear's ethereal songs in its intimacy and the focus on Rossen's lyrics. While the '60s pop-driven melodies remain intact and the heavy, washy guitars are still present, Rossen's words about his departed father and memories from childhood float above the arrangements.

"Fred's style is different and it opened up that possibility. There were tracks that would have never been on a Grizzly Bear record. In that group, the songwriting process is very communal and collaborative. ['In Ear Park'] has a thread that we arranged around, and it became a personal statement," he continues. "There was fine line we tread between being sentimental and precious. It's also hard to reveal to people things about my father's death. It's personal so it's weird, but it is such a part of it. I am very happy with the result."

The group has only played one single, full-band show and has no definitive plans to tour, a far cry from Grizzly's non-stop touring schedule, which has included stints opening for Radiohead and Feist over the last three years. Rather than spending much time capitalizing on the success of "In Ear Park, Rossen, Bear and Taylor are already onto the next thing: It is in that house in Cape Cod that the trio, plus Grizzly founder Ed Droste, are finishing recording a new Grizzly Bear effort, the follow-up to 2006's "Yellow House."

"Grizzly is my main thing. I'm happy with whatever happens with Department of Eagles, but I already have a great band."