Full disclosure: I spent the better part of my summer listening to the indie rock CDs that flooded the mailboxes I was forced to sort while I worked at a radio station. While I’m not one to complain about free stuff, the forced listening may be directly responsible for my annoyance with the Fiery Furnaces.

There was a time when I didn’t mind listening to seven-minute songs with two tempo changes in the first sixty seconds. When the Furnaces sang lyrics demanding that they notarize my will, I thought they were actually kind of brilliant. Now, I want them just to write a song I actually like.

On their sixth album, “Widow City,” the brother-sister duo of Matthew and Eleanor Friedberger continue their brand of bluesy, loosely constructed indie, going to town with the various instruments Matthew has managed to find (this includes a Chamberlin). According to the website of their new label, Thrill Jockey, the lyrics were inspired by a combination of ads from the back of early seventies design magazines, the cultural pages of local alternative lifestyle newspapers, and the Baccalieri children’s use of a Ouija board in season four of the “Sopranos.”

The music is meant to follow the lyrics’ lead: hence the thunder sounds when Eleanor is talk-singing about thunderstorms on “Ex-Guru,” and the monkey and cow noises in “The Old Hag is Sleeping” to indicate the rooster at dawn.

Again, I once would have found this charming and imaginative. But the obscure lyrics rarely coalesce into a coherent narrative and the supporting noises only detract from the rather impressive hard rock guitar of Matthew and the powerful beats of guest drummer Robert D’Amico. Songs like “Automatic Husband” and “Ex-Guru” begin with promising, tight intros, and for about a minute I experience indie bliss.

But then that damn Oujia board takes hold and the lyrics goes careening off in the wrong direction while we’re left with some flute solo or a heavy metal interlude. Very few songs can survive such abrupt transitions (Derek and the Dominoes’ “Layla” being one obvious exception) and this bipolarity often comes off as cliché.

At times on “Widow City,” the Furnaces seem to remember that being original doesn’t need to be so obvious. The standout track, “Restorative Beer,” finds the band being intelligent in its playfulness. The chorus purposely drags out the many syllables in “restorative,” suggesting that the lyrics are—for once—purposely intended to not fit in with the musical phrasing in the background.

The fact that the Fiery Furnaces actually are capable of writing quirky songs that aren’t mainstream but also aren’t contrived makes the entire project frustrating. Earlier albums, like “Blueberry Boat,” were successful not only because of Pitchfork’s praise but also because they successfully showed that lyrically-complicated, sonically-rich albums could work in a mainstream context. Although “Widow City” is a significant improvement over previous Furnaces records like “Rehearsing My Choir,” the entire project is just a little too self-aware, a little too purposely anti-mainstream—in other words, a little too indie.

—Reviewer Kimberly E. Gittleson can be reached at gittles@fas.harvard.edu.