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
Ten-string guitar has a single neck and allows all strings to be fretted. While the six-string classical guitar remains the standard and most common instrument, since 1963 ten-string guitars in similar configuration to the original Ramírez have been adopted by many classical guitarists and produced by several first-class luthiers, using both Yepes' original tuning and others. The Halo Guitars XSI is a solid body ten-string guitar with ten individual steel strings, two EMG ten-string pickups, and a Kahler ten-string tremolo bridge. XSI is an acronym for Extended Scale Instrument. Halo Guitars tunes the XSI from low to high as follows: A+D+G+C+F-B♭-E♭-A♭-C-F. Agile