This used to work for me, but after upgrading to to a new phone with Android 9 (Nokia 6.1/"Android One") and turning "Playing now" notifications off and then on, I now have notification sound for the "Now Playing" notification.
To debug I turned Vibrate, Sound and Light on and then off in the Notification settings (multiple times) and also restarted the phone just to check, but I still get the notification sound whenever a new song starts to play (YouTube Music) regardless of the setting in the app being to have no sound.
I need to have the notification turned on due to issue #63