The bass note of a chord is its lowest note. A chord’s bass note is often its root, however this is not always the case depending on voicing. When the notes of a chord are such that its root note is not the bass note, that chord is said to be inverted. When the bass note of a chord is not the chord’s root nor any of the pitches involved within the chord’s quality, that chord is called a slash chord. The name slash chord refers to its notation—a \(D\) minor chord with a root of \(B\) is notated as \(Dm/B\).

The notation of a chord can be outlined with the following context-free grammar:

\[\begin{aligned} Chord &\to Root\ Quality \mid Root\ Quality\ \texttt{/} \ Bass \\ Root &\to NoteName \\ Bass &\to NoteName \\ Quality &\to \text{maj} \mid \text{6} \mid \text{maj7} \mid \text{m} \mid \text{m6} \mid \text{m7} \mid \text{7} \mid \text{aug} \mid \text{dim} \mid \text{dim7} \mid \text{m7b5}\end{aligned}\]

where \(NoteName\) is a note name according to the context-free grammar in figure \ref{fig:cfgnote}.