From the insterests of overtone series on the piano, I made the system which makes feedbacks based on the overtone series. The system: a microphone put on the piano goes into an amplified speaker. the next microphone set up on the amplified speaker, and this microphone connected to the next amplified speaker. In this way, I made a chain of microphones and speakers. These speakers are specificly choosed for different frequency ranges to pick up certain overtones. These feedbacks create colourful drown sound pad under neath repetitive and rhythmic piano patterns.