Is there a way to play only the music checked?

Hi rik the dreamer,

Welcome to the Apple Support Communities! I'm sure we can help you out with your question, or at least get you pointed in the right direction. To play all of your checked music in iTunes (and only your checked music), the easiest way may be to create a Smart Playlist ("Checked" is one of the options when setting up the inclusion rules). For more information on creating Smart Playlists, you may find the following article helpful:

iTunes 12 for Windows: Create a Smart Playlist

Regards