|Abstract||This paper describes a real-time system for rhythm manipulation of polyphonic audio signals. A rhythm analysis module extracts information of tempo and beat location. Based on this rhythm information, we apply different transformations Tempo, Swing, Meter and Accent . This type of manipulation is generally referred as Content-based transformations. We address characteristics of the analysis and transformation algorithms. In addition, user interaction plays also an important role in this system. Tempo variations can be controlled either by tapping the rhythm with a MIDI interface or by using an external audio signal such as percussion or the voice as tempo control. We will conclude pointing out several use-cases, focusing on live performance situations.