Check out the cardboard box housing on the sewing machine synth type monstrosity above (not a Singer). As much as I admire the ad-hoc nature of the 'design' I can also see how these musical tinkerers , Circuit Benders or Zoybar types could integrate 3D printed housings, bridges, buttons, resonators, machine heads, knobs, clips and casings....
There are a vast amount of lo-fi there are some semi-professionalsynth mods that would do well to include 3D printed components to maintain a professional finish to what can be very extensive (and expensive) modification of existing instruments. There are also many Steampunk Synth Mods that would do wee to incorporate some of Shapeways new 3D printed stainless steel finishes.
If anyone has started or is planning a musical project using Shapeways let us know, we look forward to the cross pollination of the mathematic and musical minds.
Am currently planning viola and violin mutes that have been printed. The heavy practice mutes that you put on a viola/violin bridge are a big pain because they sit on top and block the view over the bridge. I've taken to slapping a couple heavy earth magnets around the bridge instead, which gives me a better view but doesn't mute as well.
I'd love to print up some pretty steel art nouveau shapes (all I need is the blasted free time) that I can tuck disc-shaped magnets into, and slap them on the sides of the bridge in pairs. I can print a simple shape and stick it on with a magnet on the other side of the bridge, but I like the idea of paired shapes. Less heavy mutes can be made of the colored plastics with slots for magnets.
You could also make a wolf eliminator. Stringed instruments often have tones that they go haywire when trying to produce called wolf tones. Cellos often have them, and one of the common cures is to stick a heavy lump of metal on the outside with putty. Put a magnet on an iced tea spoon and put it through the f-hole on the wolf side, and you can anchor a pretty printed lump of steel on the belly of the instrument that will hold still and not get lost inside it.
So there are my musical ideas -- practice mutes and wolf killers for strings.
The best thing to do is check the materials page http://www.shapeways.com/materials/
We are also developing a sample pack that includes all of the materials so you can get a feel for them yourself.
Also if you post a question on the forum about a particular material or process you are bound to get a flood of useful information from the community members who are very generous in sharing their experience.