NEWPORT, R.I. — Its producer, Jay Sweet, is fond of calling the venerable Newport Folk Festival an event for musical omnivores. Eschewing strict definitions of the genre, Sweet has expanded the scope of the programming to get the festival back to its legacy years when Newport was a beacon for American roots music.

Festival founder George Wein gave Sweet some good advice early on: For every up-and-coming band you program, book someone who likely influenced them. That approach has worked well, particularly for this year’s event, which opened Friday, closed Sunday, and sold out three months in advance.