Chord notation
Musicians use various kinds of chord names and symbols in different contexts to represent musical chords. In most genres of popular music, including jazz, pop, and rock, a chord name and its corresponding symbol typically indicate one or more of the following:
For instance, the name C augmented seventh, and the corresponding symbol Caug7, or C+7, are both composed of parts 1 (letter 'C'), 2 ('aug' or '+'), and 3 (digit '7'). These indicate a chord formed by the notes C–E–G♯–B♭. The three parts of the symbol (C, aug, and 7) refer to the root C, the augmented (fifth) interval from C to G♯, and the (minor) seventh interval from C to B♭.
Although they are used occasionally in classical music, typically in an educational setting for harmonic analysis, these names and symbols are "universally used in jazz and popular music",[1] in lead sheets, fake books, and chord charts, to specify the chords that make up the chord progression of a song or other piece of music. A typical sequence of a jazz or rock song in the key of C major might indicate a chord progression such as
This chord progression instructs the performer to play, in sequence, a C major triad, an A minor chord, a D minor chord, and a G dominant seventh chord. In a jazz context, players have the freedom to add sevenths, ninths, and higher extensions to the chord. In some pop, rock and folk genres, triads are generally performed unless specified in the chord chart.
These chord symbols are used by musicians for a number of purposes. Chord-playing instrumentalists in the rhythm section, such as pianists, use these symbols to guide their improvised performance of chord voicings and fills. A rock or pop guitarist or keyboardist might literally play the chords as indicated (e.g., the C major chord would be played by playing the notes C, E and G at the same time). In jazz, particularly for music from the 1940s bebop era or later, players typically have latitude to add in the sixth, seventh, and/or ninth of the chord. Jazz chord voicings often omit the root (leaving it to the bass player) and fifth. As such, a jazz guitarist might voice the C major chord with the notes E, A and D—which are the third, sixth, and ninth of the chord. The bassist (electric bass or double bass) uses the chord symbols to help improvise a bass line that outlines the chords, often by emphasizing the root and other key scale tones (third, fifth, and in a jazz context, the seventh).
The lead instruments, such as a saxophonist or lead guitarist, use the chord chart to guide their improvised solos. The instrumentalist improvising a solo may use scales that work well with certain chords or chord progressions, according to the chord-scale system. For example, in rock and blues soloing, the pentatonic scale built on the root note is widely used to solo over straightforward chord progressions that use I, IV, and V chords (in the key of C major, these would be the chords C, F, and G7).
In a journal of the American Composers Forum the use of letters to indicate chords is defined as, "a reductive analytical system that views music via harmonic motion to and from a target chord or tonic".[2] In 2003 Benjamin, Horvit, and Nelson describe the use of letters to indicate chord root as, "popular music ([and/specifically] jazz) lead sheet symbols."[3] The use of letters, "is an analytical technique that may be employed along with, or instead of, more conventional methods of analysis such as Roman numeral analysis. The system employs letter names to indicate the roots of chords, accompanied by specific symbols to depict chord quality."[4]
Other notation systems for chords include:[5]