I dream of the day where I could potentially have my own audio hardware startup for under a couple grand. Being able to print custom parts would make it so much more viable to make boutique audio equipment, instruments, etc.
Are you familiar with the work being done at Stanford on music? I saw a special on TV (I think it was on Nova Science Now) about the group. They are doing some interesting things in terms of making new instruments out of things they find sitting around. They also have their own "computer" symphony. Here's a link: http://ccrma.stanford.edu/overview/Overview.html