Hello there @Google UserX! 

That’s right, you have to use the Yamaha app to play music. 

But you should have access to the you deezer library, not just mp3s and 30 seconds music. 

Do you have an active subscription? 

I do have premium subscription but the Musicast app only shows and plays 30 seconds music. There's no menu to change this setting. 

Edit.

I logged in with wrong account. Now it works perfectly, can play the full songs.

Thanks for your assistance.

Best Regards.