Classical guitars, also known as "Spanish" guitars  , are typically strung with nylon strings, plucked with the fingers, played in a seated position and are used to play a diversity of musical styles including classical music. The classical guitar's wide, flat neck allows the musician to play scales, arpeggios, and certain chord forms more easily and with less adjacent string interference than on other styles of guitar. Flamenco guitars are very similar in construction, but they are associated with a more percussive tone. In Portugal, the same instrument is often used with steel strings particularly in its role within fado music. The guitar is called viola, or violão in Brazil, where it is often used with an extra seventh string by choro musicians to provide extra bass support.
The previously discussed I-IV-V chord progressions of major triads is a subsequence of the circle progression, which ascends by perfect fourths and descends by perfect fifths: Perfect fifths and perfect fourths are inverse intervals, because one reaches the same pitch class by either ascending by a perfect fourth (five semitones) or descending by a perfect fifth (seven semitones). For example, the jazz standard Autumn Leaves contains the iv7-VII7-VIM7-iiø7-i circle-of-fifths chord-progression; its sevenths occur in the tertian harmonization in sevenths of the minor scale. Other subsequences of the fifths-circle chord-progression are used in music. In particular, the ii-V-I progression is the most important chord progression in jazz music.
The shape of the neck (from a cross-sectional perspective) can also vary, from a gentle "C" curve to a more pronounced "V" curve. There are many different types of neck profiles available, giving the guitarist many options. Some aspects to consider in a guitar neck may be the overall width of the fretboard, scale (distance between the frets), the neck wood, the type of neck construction (for example, the neck may be glued in or bolted on), and the shape (profile) of the back of the neck. Other types of material used to make guitar necks are graphite (Steinberger guitars), aluminum (Kramer Guitars, Travis Bean and Veleno guitars), or carbon fiber (Modulus Guitars and ThreeGuitars). Double neck electric guitars have two necks, allowing the musician to quickly switch between guitar sounds.
the fifth, which is a perfect fifth above the root; consequently, the fifth is a third above the third—either a minor third above a major third or a major third above a minor third. The major triad has a root, a major third, and a fifth. (The major chord's major-third interval is replaced by a minor-third interval in the minor chord, which shall be discussed in the next subsection.)
Unlike many string instruments which use a bow to create a sound, guitars are played by plucking or strumming the strings on the instrument, which vibrate to create a sound. Chords are played when the guitarist holds their fingers down on more than one individual string to change its length, which in turn changes the frequency of the vibration created - in other words, it creates a different note. Performers often use guitar tabs, rather than sheet music, when learning music: this acts as a kind of 'map' to teach guitarists where to put their fingers on the strings.