Apparently Macro and Still Life is the closest forum match for instrument photography.
Here are some acoustic guitars I photographed the past few years. Some I kept, some were sold. The first time photographing was to list a small redwood top guitar then I decided to take a set of photos for any of the rest. It's a similar setup to how I photography people. Softbox on my right, strip box to the left and slightly behind. And a bare speedlight upper right near the ceiling.
Some of the woods include spruce, redwood and cedar tops. And rosewood, cherry, maple and rosewood backs.