Through designing and constructing controllers over the last 15 years, the author has developed some principles and a (loose) philosophy. These are not assumed to be universal, but are rather a set of opinions formed as part of the process of making many musical interfaces. They relate to practical issues for the modern instrument craftsperson/hacker. In this paper the author presents some observations on the design, artistic, and human factors of creating digital music controllers. Specific projects are presented, and a set of design principles are established through these examples.