The festival’s opening night had culminated with a performance by the Sun Ra Arkestra, a big band based in Philadelphia that is experiencing a late-late-career renaissance more than 20 years after the death of its namesake. But it was on Friday that audiences began to wake up and recognize the rareness of what they were hearing. The saxophonist and composer Anthony Braxton headlined, playing a solo performance that was full of a mysterious, sibilant lyricism; his playing was more beautiful and generous than usual, but it still focused your attention on the way an instrument must assign a set of linguistic parameters — and what it means to brush against them. On original pieces and, unexpectedly, covers of jazz standards (“Ruby, My Dear” and “Four”), he played little flurrying obbligatos and flights around a single note, softly splitting tones or warbling or breathing through the horn while clacking on its keys.

The flutist Claire Chase, 39, began her set earlier that night with a spellbinding extended composition for flute and electronics — darkened percussive sounds and splattering effects teasing her blustery flute from below and above. She was true to the instrument, not conveying a lot of weight or body, but exuding gravitas and a deceptive power. She ended the piece on one note, holding it and repeating it, pushing hard. It was as if she had busted a hole through the sound and was now blasting air through it, the tattered canvas flapping and shivering in the wind.

Next, Ms. Chase was joined onstage by a pickup crew of Philadelphia artists, who sat in a circle around her. On her cue they played a variety of instruments — glasses filled with water, triangles, other hand percussion — as she wove a melody throughout the pooling communal sound. Finally, they stood together, facing the audience, and Ms. Chase invited the entire room to join in singing Pauline Oliveros’s “Tuning Meditation,” whereby everyone sings tones of their own choosing while listening intently to the others’ pitch choices, creating a kind of endless circuit.

Ms. Chase was taking control of the space in a way that no other artist at the festival did, extending an invitation and embodying all the power and generosity that act implies. She was reframing the interaction, asking audience members to buy in with something other than money.