When Willow leads the group to return the baby, it makes it's big presentation and I recall it also representing Willow other times. As the Madmartigan theme seems to play mainly for Val Kilmer. I could be wrong, but the ethereal wordless choice material is for Elora.
As far as how the Schumann theme is used in the movie itself, it seems like a catch-all action/adventure theme, whether it's Madmartigan or Willow himself (but usually if Madmartigan is there so is Willow).
Xander Rodzinski has revealed on his official website that he is the composer of the fourth, fifth, sixth, seventh and eight episode of the upcoming Disney+ original series Willow. James Newton Howard is scoring the first three episodes of the show, which is developed by Jonathan Kasdan & Wendy Mericle based on Ron Howard’s 1988 feature of the same title and stars Warwick Davis, Erin Kellyman, Ellie Bamber, Ruby Cruz, Tony Revolori and Amer Chadha-Pate. The fantasy drama produced by Lucasfilm follows an unlikely group of heroes who set off on a dangerous quest to places far beyond their home, where they must face their inner demons and come together to save their world. Rodzinski has previously collaborated with Howard on numerous projects over the last couple of years, including A Hidden Life and Lucasfilm’s Light & Magic, for which he contributed additional music, and Fantastic Beasts: The Crimes of Grindelwald, News of the World and Disney’s Raya and the Last Dragon and Jungle Cruise, on which he served as the score producer. Willow is set to premiere on November 30, 2022 on Disney+.
This feels so weird. Watching a character we haven't seen in decades answer the call to help almost immediately rather than wallowing in self-pity. And it's a sequel! I don't think we'll see a Star Wars sequel that moves the franchise forward for at least a decade or two.
Once upon a time a man got Goddamn lucky with some magic acorns, gimmick magic for temporary advantage, and a parlor illusion, against a powerful sorceress. Now he's qualified to take on evil again, don't ya know.