Computers enable new possibilities in the realms of interactive art and music. Media artists are leveraging interactive mediums to create new kinds of performances and experiences. While these technologies are becoming cheaper and more ubiquitous, the barrier to entry for creating such works remains high. This dissertation presents an approach to making these technologies more accessible to a broad audience of creators, including artists, musicians and young people without technical backgrounds. The new tools and approaches introduced here lower the barrier of entry to this rapidly evolving art form. The resulting digital musical instruments and musical robots produced by novices using these tools mirror common styles of interfaces produced by practicing artists and researchers. This work shows that by supporting users in open-ended creative tasks, these design tools enable participation with sophisticated forms of musical expression.