|This article possibly contains original research. (January 2011)|
A chord chart (or chart) is a form of musical notation that describes harmonic and rhythmic information. 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 actual notes used to represent the chord and the appropriate ornamentation or counter melody.
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 any way he sees fit (called "comping"). In Nashville notation the key is left unspecified by substituting numbers for chord names.
Chord charts are similar to the figured bass ("basso continuo") system used as early as the beginning of the seventeenth century to allow the continuo ("rhythm section") keyboard to improvise right-hand chords over a written bass line played with the left hand. Since it uses key-relative "figures" rather than absolute chord-names, figured bass most closely resembles Nashville notation (described below).
Rhythmic notation specifies the exact rhythm in which to play or comp the indicated chords. The chords are written above the staff and the rhythm is indicated in the traditional manner, though pitch is unspecified through the use of slashes placed on the center line instead of notes. This is contrasted with the less specific slash notation.
Slash notation is a form of purposefully vague musical notation which indicates or requires that an accompaniment player or players improvise their own rhythm pattern or comp according to the chord symbol given above the staff. On the staff a slash is placed on each beat (so that there are four slashes per measure in 4/4 time).
Slash notation and rhythmic notation may both be used in the same piece, for example, with the more specific rhythmic notation used in a section where the horn section is playing a specific melody or rhythmic figure that the pianist must support, and with slash notation written for the pianist for use underneath improvised soli.
Nashville notation or Nashville number system is a method of writing, or sketching out, musical ideas, using numbers in place of chord names. For example, in the key of C major, the chord D minor 7 can be written as "2-7", "2m7", or "ii7".
In the key of C, C=1, D=2, E=3, and so on for all seven notes in the key. Similarly, in the key of G, G=1, A=2, B=3, and so on up to F♯=7. So, the chord progression
C///F///G///C/// in the key of C would correspond to
1///4///5///1/// in Nashville notation, while
G///C///D///G/// in the key of G would also become
This method of notation allows musicians who are familiar with basic music theory to play the same song in any key.
Chord charts in computer files
Chord charts can be represented in a schematic way as ASCII files, where bar lines are given as pipe symbols "|", chord symbols are approximated as text and beats may be indicated with a forward slash "/".
In this context, the term "chord chart" is also used to describe a lyric sheet where chord symbols are placed above the appropriate syllables of the lyrics to associate the relative timing of the chord changes to the words of a song.