This is what it sounds like when one of the greatest voices in jazz history is completely in her element. Sarah Vaughan’s live recording from the 1969 Copenhagen Jazz Festival, featuring her trio of pianist Johnny Veith, bassist Guss Mancuso, and drummer Ed Pucci, is a 15-song document of an artist operating at the peak of her powers, moving through classics like “Fly Me to the Moon,” “Misty,” “Body & Soul,” and “All of Me” with the kind of effortless authority that made her one of the most celebrated vocalists of the 20th century. If you haven’t heard this, clear your afternoon.