A song accompaniment system includes a karaoke machine and a simulated guitar machine, and the karaoke machine downloads accompanying music in the form of MIDI data from a source data storage. Of the MIDI data downloaded from the source data storage, a simulative instrument part of the accompanying music is transferred to the simulated guitar machine. In the simulated guitar machine, an allocation processor allocates individual sounds of the simulative instrument part to three scroll bars in a guidance picture which is presented on a monitor of the simulated guitar machine, and operating timing for producing the individual sounds is indicated by note marks which are scrolled along the scroll bars. When a player plays a simulated guitar, tone waveforms contained in the MIDI data received from the source data storage are modulated and an audio signal thus generated is output from speakers. If the simulated guitar is correctly operated, the accompanying music is reproduced in proper fashion.