In this paper, a new concept of real-time loop music production is introduced, along with its implementation in Pd. This scheme tends to improvise loop music based on very limited pattern (loop sample) materials. Four loops, each divided into 32 grains, work at the same time. Analysis of the spectral and energy similarities between every two grains are conducted, and the transition probability matrices generated by the analysis phase are consulted for each decision of grain choice during remixing. A joystick-style controller is designed to control the probability distribution, which changes the music characteristics in real-time. While maintaining some characteristics of each loop pattern, the music generated by the program reveals a large space of variations and controllable improvisations. Real-time analysis is considered, that later will enable switching new patterns into the 4pattern group during a performance. This scheme is a potential new method for live computer DJ mixing in the loop pattern level. Sound examples, including four drum loops and the improvisations on them, can be found at http://crca.ucsd.edu/˜pxiang/granuloop.htm

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