hobbyists playing folk music around a campfire are well served by standard tuning. Such hobbyists may also play major-thirds tuning, which also has many open chords with notes on five or six strings; chords with five-six strings have greater volume than chords with three-four strings and so are useful for acoustic guitars (for example, acoustic-electric guitars without amplification). Intermediate guitarists do not limit themselves to one hand-position, and consequently open chords are only part of their chordal repertoire. In contemporary music, master guitarists "think diagonally and move up and down the strings"; fluency on the entire fretboard is needed particularly by guitarists playing jazz. According to its inventor, Ralph Patt, major-thirds tuning makes the hard things easy and the easy things hard. ... This is never going to take the place of folk guitar, and it's not meant to. For difficult music, and for where we are going in free jazz and even the old be-bop jazz, this is a much easier way to play. Left-handed chords Major-thirds tuning is closely related to minor-sixths tuning, which is the regular tuning that is based on the minor sixth, the interval of eight semitones. Either ascending by a major third or by descending by a minor sixth, one arrives at the same pitch class, the same note representing pitches in different octaves. Intervals paired like the pair of major-third and minor-sixth intervals are termed "inverse intervals" in the theory of music. Consequently, chord charts for minor-sixths tunings may be used for left-handed major-thirds tunings; conversely, chord charts for major-thirds tunings may be used for left-handed minor-sixths tunings. Fingering of seventh chords Major-thirds tuning facilitates playing chords with closed voicings. In contrast, standard tuning would require more hand-stretching to play closed-voice seventh chords, and so standard tuning uses open voicings for many four-note chords, for example of dominant seventh chords. By definition, a dominant seventh is a four-note chord combining a major chord and a minor seventh. For example, the C7 seventh chord combines the C-major chord {C, E, G} with B. In standard tuning, extending the root-bass C-major chord (C,E,G) to a C7 chord (C, E, G, B) would span six frets (3–8); such seventh chords "contain some pretty serious stretches in the left hand". An illustration shows this C7 voicing (C, E, G, B), which would be extremely difficult to play in standard tuning, besides the openly voiced C7-chord that is