Dave Grohl said that the making of the Foo Fighters' upcoming TV show and album was a “complicated process” as they toured across America, recording and finding inspiration along the way.

The HBO documentary series, ‘Sonic Highways,’ will chronicle the Foo Fighters as they travel to eight historic music cities around the country and talk to local musicians, learning about regional genres and recording the album along the way.

It's all pretty ambitious, as Grohl and bandmate Taylor Hawkins confirmed to Rolling Stone South Africa in a new interview. After talking to local artists, Grohl said, he'd be inspired to write a song just moments before the band recorded it.

"I don't write the words until the day before I sing them, sometimes that morning,” he admitted. "It's also a relief, because I'm pulling direct inspiration [from my surroundings]."

But for Hawkins, working alongside local musicians made him feel like he was "hanging on for dear life," he sais. "[When they're] next to me, playing the craziest upside-down stuff, I just [try] to keep time."

The Foos recorded in Chicago, Nashville, Austin, Seattle and Washington, DC, among other cities. Grohl told the magazine that he originally wanted to record and film worldwide in cities like Johannesburg and Sao Paulo, but that was “financially impossible” in the end.

The upcoming album is expected to include only eight tracks, but don’t worry. Grohl insisted that "it's gonna be our longest album. There are some epic jams."

Release dates for the album and series haven't been set yet, but they're both expected to come out sometime around October, just in time for the Foos' 20th anniversary.

While we wait, here's the teaser trailer for 'Sonic Highways':