This paper is a study of the unique problems posed by the use of computers by composers and performers of music. The paper begins with a presentation of the basic concepts involved in the musical interaction with computer devices, followed by a detailed discussion of three musical tasks: music manuscript preparation, music language interfaces for composition, and real-time performance interaction. Fundamental design principles are exposed through an examination of several early computer music systems, especially the Structured Sound Synthesis Project. A survey of numerous systems, based on the following categories, is presented: compositions and synthesis languages, graphics score editing, performance instruments, digital audio processing tools, and computeraided instruction in music systems. An extensive reference list is provided for further study in the field.