[Problem] To enable a sound bar and a wireless speaker to be grouped and ungrouped through a simple operation. [Solution] When a user moves a controller 3 closer to a sound bar 1. the sound bar 1 reads tag information from an RFID tag 30 of the controller 3 by using an RFID tag reader 10. detects that the user has performed an operation to move the controller 3 closer to the sound bar 1, and checks a host group state. When group formation is in progress, an ungroup notification is transmitted to a wireless speaker 2, which is a participating member of the group. to ungroup the group. and information relating to a slave of the ungrouped group is stored as immediately preceding slave information. However, when ungrouping is in progress. a group formation notification is transmitted to the wireless speaker 2 identified by the immediately preceding slave information to form a group with the wireless speaker 2.