From Garcia’s pinky, down; between his hand and John Kahn’s headstock; his face, up: the rule of thirds.
John Kahn, Mrs. Donna Jean, and Garcia are certainly not as close as they seem to one another: foreshortening.
The brilliant white glow of the headstock and Garcia’s forehead against the ink-black background: chiaroscuro.
The arm, the bass neck, and Wolf: balance.
Your eye starts on the “Fender” and the tunings pegs, then travels upward–clockwise–to Garcia’s face, continuing down Mrs. Donna Jean’s arm to Wolf and then up Garcia’s forearm: the Fibonacci spiral.
This is Renaissance art.