Chord symbol in the context of "Consonance and dissonance"

A chord chart (or chart) is a form of musical notation that describes the basic harmonic and rhythmic information for a song or tune. It is the most common form of notation used by professional session musicians playing jazz or popular music. It is intended primarily for a rhythm section (usually consisting of piano, guitar, drums and bass). In these genres the musicians are expected to be able to improvise the individual notes used for the chords (the "voicing") and the appropriate ornamentation, counter melody or bassline.

In some chord charts, the harmony is given as a series of chord symbols above a traditional musical staff. The rhythmic information can be very specific and written using a form of traditional notation, sometimes called rhythmic notation, or it can be completely unspecified using slash notation, allowing the musician to fill the bar with chords or fills any way they see fit (called comping). In Nashville notation the key is left unspecified on the chart by substituting numbers for chord names. This facilitates on-the-spot key changes to songs. Chord charts may also include explicit parts written in modern music notation (such as a musical riff that the song is dependent on for character), lyrics or lyric fragments, and various other information to help the musician compose and play their part.

In music, a ninth is a compound interval consisting of an octave plus a second.

Like the second, the interval of a ninth is classified as a dissonance in common practice tonality. Since a ninth is an octave larger than a second, its sonority level is considered less dense.

Jazz chords are chords, chord voicings and chord symbols that jazz musicians commonly use in composition, improvisation, and harmony. In jazz chords and theory, most triads that appear in lead sheets or fake books can have sevenths added to them, using the performer's discretion and ear. For example, if a tune is in the key of C, if there is a G chord, the chord-playing performer usually voices this chord as G. While the notes of a G chord are G–B–D–F, jazz often omits the fifth of the chord—and even the root if playing in a group. However, not all jazz pianists leave out the root when they play voicings: Bud Powell, one of the best-known of the bebop pianists, and Horace Silver, whose quintet included many of jazz's biggest names from the 1950s to the 1970s, included the root note in their voicings.

Improvising chord-playing musicians who omit the root and fifth are given the option to play other notes. For example, if a seventh chord, such as G, appears in a lead sheet or fake book, many chord-playing performers add the ninth, thirteenth or other notes to the chord, even though the lead sheet does not specify these additional notes. Jazz players can add these additional, upper notes because they can create an important part of the jazz sound. Lead sheets and fake books often do not detail how to voice the chord because a lead sheet or fake book is only intended to provide basic guide to the harmony. An experienced comping performer playing electric guitar or piano may add or remove notes as chosen according to the style and desired sound of that musician, but must do so in a way that still emphasizes the correct musical context for other musicians and listeners.