Eight-string guitar

[4][6] Luthier Saul Koll modified a sequence of guitars: a 1938 Gibson Cromwell, a Sears Silvertone, a c. 1922 Mango archtop, a 1951 Gibson L-50, and a 1932 Epiphone Broadway; for Koll's modifications, custom pick-ups accommodated Patt's wide necks and high G♯ (equivalently A♭);[6] custom pick-ups were manufactured by Seymour Duncan[6] and by Bill Lawrence.

[4] Roy Connors, former member of the 1960s folk singing group, The Highwaymen, reconfigured a Martin O-28 six-string guitar to an eight-string of his own design and received a U.S. Patent on it (#3269247).

[citation needed] The main design issue faced with an eight-string guitar is tuning stability with the lower strings.

Some bridge designs accommodate this by offsetting back the 7th and 8th strings or providing a bit extra room for adjustment.

[9] The eight-string guitar is used by modern heavy metal guitarists such as Fredrik Thordendal and Mårten Hagström of Meshuggah, Dino Cazares of Fear Factory, Stephen Carpenter of Deftones, Greg Burgess of Allegaeon, Simon Girard and Kevin Chartré of Beyond Creation, Justin Lowe and Trent Hafdahl of After the Burial, Josh Travis of Emmure (ex-The Tony Danza Tapdance Extravaganza and ex-Glass Cloud), Per Nilsson of Scar Symmetry and Meshuggah as a touring member and others.

Tosin Abasi and Javier Reyes of Animals as Leaders primarily use a drop-E tuning (where the lowest string matches the E1 on a standard-tuned bass guitar) and incorporate "thumping," an adaptation of different bass guitar techniques — the term blankets all sorts of possible note groupings, but primary influences include a style á la funk bassist Larry Graham and Victor Wooten's double thumping technique — as well as harp-like arpeggios extending across the full range of the instrument.

Rusty Cooley tunes his eight-string guitar like a standard six-string expanded in both directions.

This tuning offers both deeper bass tones than a conventional guitar and extended range in the higher register for lead melodies.

Chris Andrews of the death metal band Devourment uses eight-string guitars, starting with the album Obscene Majesty.