Coming from a Gizmodo interview with producer Jason Michael Paul...
Working with Nintendo on the concert series
"Once the work is submitted and revisions (if any) are made, then we only collaborate further on new submissions. Mr. Kondo and Mr. Aonuma oversee everything and anything that is performed as part of The Legend of Zelda: Symphony of the Goddesses — it is as first-party as it gets."
The three main steps of putting the show together
"...reimagining the scores to sound amazing being performed by an orchestra and choir, hiring truly talented humans that are equally as passionate about Zelda as they are about arranging and composing, [and] using a lot of the themes and melodies and making them sound bombastic and big-sounding."