A computerized method and apparatus for creating a scratch effect through a MIDI interface. In one form, timing signals are derived from a turntable whose direction and speed of rotation are manually controlled by a disk jockey. The timing signals are processed by a microcomputer into a MIDI protocol recognizable by a conventional MIDI instrument. Preferably, the microcomputer is coupled to control a computer which interprets the MIDI protocol output and uses the output to regulate speed and direction of playback of a musical and/or visual presentation.