The principal of the rotary kettledrum for orchestral use, known since 1821, has been combined in the Sonor rotary timpani with a tried-and-tested system of central tuning. The technical advantage of the Sonor timpani lies in the unimpeded transfer of vibration from the head to the shell. It is important that there should be no contact between the rods holding the tensioning screws and the shell itself. In Sonor timpani, the upper part of the drum is free of any screw mechanism. This construction is based on over 100 years' of experience.