Interactive paper technologies offer new opportunities for supporting the highly individual practices of creative artists, such as contemporary music composers, who express and explore their ideas on both paper and the computer. We introduce PaperComposer, a graphical interface builder that allows users to create a personalized interactive paper interface that they can connect to their own computer-based musical data. We also present an API that facilitates the development of interactive paper components for PaperComposer. We describe one public demonstration of a novel musical interface designed for children and our collaborations with composers to create two novel interactive music interfaces that reflected their individual composition styles.