Multiple part-link elements can reference different types of linked documents, such as parts and condensed score. The optional group-link elements identify the groups used in the linked document. The content of a group-link element should match the content of a group element in the linked document.
The
<group-link>element.Multiple part-link elements can reference different types of linked documents, such as parts and condensed score. The optional group-link elements identify the groups used in the linked document. The content of a group-link element should match the content of a group element in the linked document.
See
https://www.w3.org/2021/06/musicxml40/musicxml-reference/elements/group-link/