The disclosure relates to control and audio manipulation of a digital audio signal by a user manipulable rotary control. The disclosure is specifically applicable to manipulation of a digital audio signal by disc jockeys (DJs). A magnet and corresponding sensor are used to obtain rotational state information from the turning of the user manipulable rotary control. This rotational state information is used to manipulate a digital audio signal. Manipulation of the digital audio includes forward and backward motion as well as a “scratch effect”. Rotational state information obtained from rotating magnet includes the possibility of absolute rotation position as well as relative rotational position, or rotational direction.