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
Vibrato systems for guitar An advantage or disadvantage, depending on taste, is string resonance audible at several fret positions where a simple relation exists between the length to the fret and the string length behind the bridge (for instance 48:12 = 4:1). At those positions, a high overtone rises in volume. This becomes clearer with an over-driven guitar sound. The overtone might sound odd, but it still has a harmonic relation to the note, so is not out of tune related to the open string. For staccato playing, it can be annoying. Muting the strings behind the bridge with felt or other material solves