sequences of third intervals; progressions are occasionally based on sequences of second intervals. Extended chords As their categorical name suggests, extended chords indeed extend seventh chords by stacking one or more additional third-intervals, successively constructing ninth, eleventh, and finally thirteenth chords; thirteenth chords contain all seven notes of the diatonic scale. In closed position, extended chords contain dissonant intervals or may sound supersaturated, particularly thirteenth chords with their seven notes. Consequently, extended chords are often played with the omission of one or more tones, especially the fifth and often the third, as already noted for seventh chords; similarly, eleventh chords often omit the ninth, and thirteenth chords the ninth or eleventh. Often, the third is raised an octave, mimicking its position in the root's sequence of harmonics. Dominant ninth chords were used by Beethoven, and eleventh chords appeared in Impressionist music. Thirteenth chords appeared in the twentieth century. Extended chords appear in many musical genres, including jazz, funk, rhythm and blues, and progressive rock. Chord guide for major and minor 9 chords (Standard tuning, read from left to right, low E to high e) Major 9 AM9: [XX7454] BbM9: [XX8565] BM9: [XX9676] CM9: [XX(10)787] C#M9: [XX(11)898] DM9: [XX0220] EM9: [099800] FM9: [XX3010] GM9: [XX5232] Minor 9 Am9: [575557] Bm9: [797779] Cm9: [X3133X] Dm9: [X5355X] Em9: [X7577X] Fm9: [X8688X] Gm9: [353335] Alternative harmonies Scales and modes Conventional music uses diatonic harmony, the major and minor keys and major and minor scales, as sketched above. Jazz guitarists must be fluent with jazz chords and also with many scales and modes; "of all the forms of music, jazz ... demands the highest level of musicianship—in terms of both theory and technique". Whole tone scales were used by King Crimson for the title track on its Red album of 1974; whole tone scales were also used by King Crimson guitarist Robert Fripp on "Fractured". Beyond tertian harmony In popular music, chords are often extended also with added tones, especially added sixths. Quartal and quintal harmony Chords are also systematically constructed by stacking not only thirds but also fourths and fifths, supplementing tertian major–minor harmony with quartal and quintal harmonies. Quartal and quintal harmonies are used by guitarists who play jazz, folk, and rock music. Quartal harmony has been used in jazz by guitarists such as Jim Hall (especially on Sonny Rollins's The Bridge), George Benson ("Skydive"), Kenny Burrell ("So What"), and Wes Montgomery ("Little