If your audio or video master includes timer support you can use it to start playing N.MUSIC or N.RADIO like you do with any other source. Refer to your products documentation for how to program the timer.
For N.MUSIC the program option means which playlist to start playling. The Library playlist is number 1. For N.RADIO the program options means which channel in the N.RADIO playlist to play.The timer functionality works even if the computer is sleeping.