The root-alter element represents the chromatic alteration of the root of the current chord within the harmony element. In some chord styles, the text for the root-step element may include root-alter information. In that case, the print-object attribute of the root-alter element can be set to no. The location attribute indicates whether the alteration should appear to the left or the right of the root-step; it is right by default.
The
<root-alter>element.The root-alter element represents the chromatic alteration of the root of the current chord within the harmony element. In some chord styles, the text for the root-step element may include root-alter information. In that case, the print-object attribute of the root-alter element can be set to no. The location attribute indicates whether the alteration should appear to the left or the right of the root-step; it is right by default.
See
https://www.w3.org/2021/06/musicxml40/musicxml-reference/elements/root-alter/