Meshuggah pioneered it, Periphery took it to new levels, and John Petrucci thinks it opens up "a new world" – here is everything you need to know about learning 8-string guitar

When Swedish metal icons Meshuggah unleashed their mighty, low down, single-string riffs on Nothing in 2002, the meaning of the word heavy was henceforth redefined. From then, the 8-string guitar has gradually gained more popularity in the progressive metal sphere, with bands like Periphery, Animals as Leaders, Dream Theater and Sleep Token underpinning their music with the extended range of the instrument.

Simply put, the 8-string is a 6-string with two extra low strings. The most common tuning from low to high is F# B E A D G B E (that is, standard guitar tuning with low B and F# strings). There is also a drop E version for extra heaviness (low to high): E B E A D G B E. Pitch-wise, this essentially takes the 8-string guitar into bass guitar territory, but the lighter string gauge and the various pickup options lend it a different sonic character.