In its almost 50 years of existence the field of computer music has brought us dozens of software systems, and new ones are still being added. This is a sign of the fields vitality and of constant interest in improving the tools that are used in order to make music on computers. This work is primarily an overview of existing systems, from a conceptual point of view, in an attempt to extract the essence of computer music systems and to pinpoint the software models that work best in the computer music domain. The criteria are °exibility, speed and - drawn from human computer interaction - intuitiveness of the programming model. Secondarily it is a review of my research work in this direction and finally an attempt to reassemble the best ide...