Sun light. This photo looks like it was taken at dusk or dawn and it’s dark enough to see the far side/day side of earth reflecting more than the night side. It’s not as noticeable for us with Venus because it’s closer ie brighter and more reflective due to the atmosphere making it visibly white.

For guitarists definitely ‘wooden heads’ cus different woods are their outlet.

But they’re almost all ‘iums’, changing just one is like finding a fly in a bowl of cereal