different strings. Many chords can be played with the same notes in more than one place on the fretboard. Musical fundamentals The theory of guitar-chords respects harmonic conventions of Western music. Discussions of basic guitar-chords rely on fundamental concepts in music theory: the twelve notes of the octave, musical intervals, chords, and chord progressions. Intervals The octave consists of twelve notes. Its natural notes constitute the C major scale, (C, D, E, F, G, A, B, and C). The intervals between the notes of a chromatic scale are listed in a table, in which only the emboldened intervals are discussed in this article's section on fundamental chords; those intervals and other seventh-intervals are discussed in the section on intermediate chords. The unison and octave intervals have perfect consonance. Octave intervals were popularized by the jazz playing of Wes Montgomery. The perfect-fifth interval is highly consonant, which means that the successive playing of the two notes from the perfect fifth sounds harmonious. A semitone is the distance between two adjacent notes on the chromatic circle, which displays the twelve notes of an octave. As indicated by their having been emboldened in the table, a handful of intervals—thirds (minor and major), perfect fifths, and minor sevenths—are used in the following discussion of fundamental guitar-chords. As already stated, the perfect-fifths (P5) interval is the most harmonious, after the unison and octave intervals. An explanation of human perception of harmony relates the mechanics of a vibrating string to the musical acoustics of sound waves using the harmonic analysis of Fourier series. When a string is struck with a finger or pick (plectrum), it vibrates according to its harmonic series. When an open-note C-string is struck, its harmonic series begins with the terms (C,C,G,C,E,G,B,C). The root note is associated with a sequence of intervals, beginning with the unison interval (C,C), the octave interval (C,C), the perfect fifth (C,G), the perfect fourth (G,C), and the major third (C,E). In particular, this sequence of intervals contains the thirds of the C-major chord {(C,E),(E,G)}. Perfect fifths The perfect-fifth interval is featured in guitar playing and in sequences of chords. The sequence of fifth intervals built on the C-major scale is used in the construction of triads, which is discussed below. Cycle of fifths Concatenating the perfect fifths ((F,C), (C,G), (G,D), (D,A), (A,E), (E,B),...) yields the sequence of fifths (F,C,G,D,A,E,B,...); this sequence of fifths displays all the notes of