Foo Fighters

The Foo Fighters' "Sonic Highways" project is much more than an album. It's like a doctoral thesis that rocks.

The companion series on HBO, which was directed by singer-drummer-guitarist Dave Grohl, traces the process of recording the album in music hot spots around the country. Each of the album's eight songs was recorded in a different city, with local artists involved and, theoretically, the local flavor seeping into the music.

That leads to the bits of Chicago blues and power pop that color the epic single "Something from Nothing." It brings some country inflection into "Congregation," which was recorded in Nashville with the Zac Brown Band. And there's a lot of hardcore rage in "The Feast and the Famine," recorded in Washington, D.C.

Grohl calls the album a "love letter to American music," and all that love shows, much as it did in his directorial debut, "Sound City," the documentary of the Southern California recording studio of the same name. Like that project, "Sonic Highways" is wildly ambitious -- a hard musical trick, as well as a way to keep things fresh for the band's eighth album, as the Foos celebrate their 20th anniversary.

After all, their bedrock sound hasn't changed much over the years -- based on Grohl's distinctive vocals, potent drumming and grand guitar solos.

But on "Sonic Highways," they layer other influences onto that base more blatantly than in the past. "In the Clear" balances indie-rock grandeur, a la Smashing Pumpkins, and the chugging guitar simplicity that has been the hallmark of many a Foos hit. On "Outside," you can almost imagine them listening to R.E.M.'s "Murmur" and Blue Öyster Cult's "(Don't Fear) The Reaper" while they worked on the song.

The problem with "Sonic Highways," though, is you can almost hear the pressure of making it. There's a lot of joy in the music, but there seems to be a lot of worry in the lyrics. After all, Grohl had to write the lyrics to these songs at the last minute in the city where they were recording.

There are times that make you wonder what it would have sounded like if they'd had more time and weren't working it out on camera with marketing deadlines and cross-promotional issues looming in the distance.

That said, it is truly great, considering the circumstances.