The numeral-mode type specifies the mode similar to the mode type, but with a restricted set of values. The different minor values are used to interpret numeral-root values of 6 and 7 when present in a minor key. The harmonic minor value sharpens the 7 and the melodic minor value sharpens both 6 and 7. If a minor mode is used without qualification, either in the mode or numeral-mode elements, natural minor is used.
The
<numeral-mode>element.The numeral-mode type specifies the mode similar to the mode type, but with a restricted set of values. The different minor values are used to interpret numeral-root values of 6 and 7 when present in a minor key. The harmonic minor value sharpens the 7 and the melodic minor value sharpens both 6 and 7. If a minor mode is used without qualification, either in the mode or numeral-mode elements, natural minor is used.
See
https://www.w3.org/2021/06/musicxml40/musicxml-reference/elements/numeral-mode/