When the GO:PIANO88 (GO-88PX) is connected to the Roland Piano App, music data provided by Roland Cloud is played on your mobile device.
To output the playback sound through the onboard speakers of the GO:PIANO88 (GO-88PX), connect via Bluetooth Audio by following the instructions in the GO:PIANO88 (GO-88PX) Reference Manual under “Setting up Bluetooth audio for the first time (Bluetooth pairing)”.