Foo Fighters recorded ‘Sonic Highways’ in eight different cities across the United States, and in a new video testimonial, frontman Dave Grohl reveals the unique way he wrote the lyrics for the songs on the disc.

In an online segment for 'The Tonight Show Starring Jimmy Fallon' (watch above), Grohl gave an in-depth description of how he penned the song ‘I Am a River,’ as well as the method he used for most of the tracks on ‘Sonic Highways.

The frontman explains that the band would spend the first few days in each city tracking in the studio, while at night he would conduct interviews with local music legends. Around the fifth day, Grohl would sit down with the transcripts from his interviews and his outline for the specific song he wanted to write.

He says he would then “sort of cut and paste” keywords, phrases and excerpts from those chats, adding them into the song outline. Grohl further explains, “The next day I would go sing the new lyric, and it was meant to represent that whole week that we'd been there by telling the stories of the people that I'd talk to."

Grohl also speaks about a general theme he started to notice as he conducted interviews across the nation, saying, “When I interviewed all these people around the country for the ‘Sonic Highways’ project, I started to realize that everyone is connected and that it is like one big family tree or community. Whether it’s Dolly Parton or Chuck D or Joan Jett or Zach Brown, whatever it is, everyone is kind of connected by something.”

Foo Fighters kick off 2015 with international tour dates starting on Jan. 15; they bring their music stateside on July 4 to Washington, D.C. See their full list of North American tour dates here.

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