This article explains how to select discs.

When Playback is Stopped

Use the DISC SELECT buttons to select a disc. Playback will start automatically.

Or, use the [DISC SKIP] button or the remote controller’s DISC [+] and [–] buttons to select a disc. In this case you’ll need to press the PLAY button to start playback.

During Playback

Use the DISC SELECT buttons, [DISC SKIP] button, or the remote controller’s DISC [+] and [–] buttons to select a disc. The current disc will stop playing, and the newly selected disc will be played.

On the display, the number of the current disc has a circle around it.