Some artists, when painting on location, listen to music through their earbuds or headphones using an iPod or similar devices. Me, I usually bring my ten-piece harp ensemble with me when I paint en plein air. Something about the angelic background music triggers Divine inspiration.
....which doesn't necessarily translate to a better painting unfortunately, but I find it soothing nonetheless. Except when you're painting here in the Fair Oaks Village, periodic interruption by roosters crowing at the top of their lungs sort of ruins the effect.