In this book you will find three algorithms for separating the audio waveform of instruments in musical performances. Each of these algorithms uses stereo cues and makes some assumptions about the structure of music in order to exploit the resulting redundancy of the tones and to localize the instruments in space. Much detail is given on the development of the algorithms, ranging from the idea at the beginning with the initial assumptions to the final algorithm. Suggestions for fine tuning are presented along with extension ideas for each algorithm in part. A separate chapter is focusing on implementation details showing ways to get the maximum speed out of the available hardware and software. A review of the state of the art algorithms in scientific literature is also included along with the common problems encountered. The lack of tools to consistently evaluate the separation quality is considered and consequently two subjective quality criteria are introduced together with a new testing corpus.