Seven-string guitar string is augmented with a high octave string. Many of McGuinn's notable guitar solos utilize the G string of the twelve-string guitar to perform the main melody, and therefore the Martin seven-string guitar was designed to achieve this extended range playing without the need for doubling all six of the guitar's strings. In 2010, Inox Guitars has created a mix of the Brazilian Viola caipira and the Russian semistrunka (семиструнка). This instrument has 2 bass strings (as the 6th and 7th strings of the semistrunka) and five treble courses (as the Viola caipira) and it is used in open tuning
Eight-string guitar Novax Guitars. Five of the strings are tuned to the standard guitar's upper five (A, D, G, B, E), while three of the strings are tuned to the standard bass guitar's three lowest (E, A, D). The bass and treble sections have separate pickups and are sent to separate amplifiers. Hunter also has a ten-string guitar based on the same principle—a combination of standard six-string guitar and standard four-string bass. 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