Intervals’ Aaron Marshall joins forces with Marco Sfogli for this awe-inspiring progressive playthrough

Instrumental prog luminaries Intervals are back, unleashing new album, Circadian, this Friday (November 13) – and to celebrate, Guitar World is premiering a playthrough of one of the album’s standout tracks.

String Theory sees Aaron Marshall deploy his trademark blend of seven-string hooks ’n’ chug, a sonic formula that verges on djent, but tempered by a melodic sensibility that sets it apart from his contemporaries.

The track is also notable for the appearance of Italian virtuoso Marco Sfogli at the 2:29 mark, who rocks up with a gorgeous satin pink Charvel for a mind-blowing, tap-heavy solo, before Marshall sends the song packing with some ultra-tight palm-muting.

Marshall’s core rig for the recordings featured a Bare Knuckle Silo-loaded Mayones Regius Core 7, Abasi J Larada 7, and a host of Neural DSP plugins, including the Fortin Cali Suite and Archetype: Nolly.

“String Theory was the last song I composed for the new record,” Marshall says. “It was one of those tunes that just sort of wrote itself – rare – and when I got to laying out the solo section, I knew I wanted a feature for this one. I reached out to one of my all-time favorite guitar heroes and shot my shot.

“Marco hit me back and told me he loved the tune and was excited to whip something up. Needless to say, I was TRIPPING OUT, haha! He sent me back an absolutely immaculate solo in under 48 hours... I was, and am still SO stoked to feature an absolute legend on this song. It really put this one over the top for me. Major bucket list moment achieved.

“Shout out to Marco for being a class act and an unbelievable musician. I’ve been channeling and interpreting his approach to the instrument in my own way for years now. Such a huge inspiration for me. I hope everyone enjoys this one!”

Circadian is out on November 13, and available to preorder now.

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Michael Astley-Brown

Mike is Editor-in-Chief of, in addition to being an offset fiend and recovering pedal addict. He has a master's degree in journalism from Cardiff University, and over a decade's experience writing and editing for guitar publications including MusicRadar, Total Guitar and Guitarist, as well as 20 years of recording and live experience in original and function bands. During his career, he has interviewed the likes of John Frusciante, Chris Cornell, Tom Morello, Matt Bellamy, Kirk Hammett, Jerry Cantrell, Joe Satriani, Tom DeLonge, Ed O'Brien, Polyphia, Tosin Abasi, Yvette Young and many more. In his free time, you'll find him making progressive instrumental rock under the nom de plume Maebe.