The microcomputer 24 (for example a single board computer) can trigger the playing of the music by emitting pulses to the 5-Volt-Clock-input 21B of the MIDI-interface 21 or simpler MIDI--timing clock codes to MIDI-in 21B. The use of microcomputer 20 (for example a PC or home computer) for the input and processing of pulses 33A, 33B and 34 and other inputs described below is more economical, becaus