Harmony parts sound boring alone and essential together. Plenty of good leaders sing harmony.

A harmony line on its own sounds thin and slightly pointless, and the same line under a melody is what makes the whole thing full. Some people work that way: unremarkable in isolation, and the reason everything else holds. Leading does not always mean carrying the tune. A good deal of it is supporting somebody else’s, accurately and without needing to be heard as the soloist.

Find out what your group is trying to do and ask where the support is thin. Take that part for a while instead of the visible one. Notice whether you can do it without needing credit.