Music streams in the music, so it might not start exactly at the same time as your layout starts when using "on layout begin"
You can import your music as a "sound" instead, and use the preload option so that it all loads up before triggering the start of your new layout. However this will result in a longer initial loading time of your game because it has to load up your entire music track before the game begins. (Your loading times might not matter for a school project, but its what you need to do if you want the music to start immediately when the layout loads.