OnSong has the ability to display chord diagrams for chords found in text-based chord charts. By default, OnSong finds the default variation of the chord in the Chord Diagram Library. In some cases you want to use a specific chord variation for a song. To do this, you define a chord using the ChordPro syntax as follows:

{define: E5 base-fret 7 frets 0 1 3 3 x x fingers - 1 2 3 - - key E}

This expression can be divided into the following parts:

Define begins the declaration of a new chord diagram.

E5 is the name of the chord that is declared. Chords matching this name will use the specified diagram. base-fret declares that the following number will be the the fret on which the chord diagram begins. All frets are relative to this base fret.

frets declares that the following will be a space-delimited list of the frets to play. In the example given, 0 means an open string is to be played, 1 and 3 are the first and third fret relative to the base fret and „x“ means to not play the that string.

fingers declares a space-delimited list of the fingers to use on each string. In this particular example, the – symbol indicates that the strings are not played with fingers. The 1, 2 and 3 indicate the fingers to be used for playing the chord.

key is the key in which the chord should be played. Not currently supported.

If the chord definition does not exist in the Chord Diagram Library, it is added and set as the default variation for the song. OnSong applies the chord to the guitar instrument when six strings are defined, the 5-string bass when five strings are defined, and the default instrument when 4 or another number of strings are used.