To support the work to find out the partners for making duet of a KARAOKE sing-along machine.
Accompaniment data of musical pieces is accumulated in a system host 10. KARAOKE sing-along machine terminals (20a, 20b, etc.), perform playing of musical pieces in accordance with the accompaniment data forwarded through a communication circuit 30 from the system host 1. The system host 10 extracts the candidates of the partners of the duet complying with the requests from the respective users respectively using the plural KARAOKE sing-along machine terminals (20a, 20b, etc.), according to the requests for the introduction of the partners for making the duet. The KARAOKE sing-along machine terminals (20a, 20b, etc.), presents the information on the candidates of the partners of the duet which are the results of the extraction to the users using the KARAOKE sing-along machine terminals (20a, 20b, etc.).