Abstract: A transmitter (2) is arranged on an acoustic drum to transform wave motions generated by hits on the drumhead (10) in electrical signals. The transmitter (2) comprises a vibration sensitive body (8) designed to be elastically forced against the drumhead (10). According to a first aspect on the invention the vibration sensitive body (8) has got an oblong shape (L:W) for detection of wave motions of a predetermined direction and within a predetermined frequency range. Another aspect on the invention is to avoid the risk of mechanical damages to the vibration sensitive body (8) as well as to emphasize the ability to detect the wave motions in the drumhead (10). This is implemented by a holder (3) being fixable to the edge (5) of the drum rim (6). The holder (3) includes an elastic spring device (12, 13) carrying the vibration sensitive body (8).