The bass type is used to indicate a bass note in popular music chord symbols, e.g. G/C. It is generally not used in functional harmony, as inversion is generally not used in pop chord symbols. As with root, it is divided into step and alter elements, similar to pitches. The arrangement attribute specifies where the bass is displayed relative to what precedes it.
The
<bass>element.The bass type is used to indicate a bass note in popular music chord symbols, e.g. G/C. It is generally not used in functional harmony, as inversion is generally not used in pop chord symbols. As with root, it is divided into step and alter elements, similar to pitches. The arrangement attribute specifies where the bass is displayed relative to what precedes it.
See
https://www.w3.org/2021/06/musicxml40/musicxml-reference/elements/bass/