YouTube has a great feature, it let you create playlists, you can add any video in your playlist. You can create playlists as many as you need. And you can add songs in a playlist as many as you need.
In a playlist you can songs as your favorite songs or sad songs or any video.

To create a playlist you must be logged in. At top right corner click on your user name, a drop down menu will be shown, there click on “My Videos”.

You will be redirected to my videos page, here at bottom right look for playlists, there click on new.

Now you have created your playlist, it is time add a song to your play list. Search your favorite song in search bar near YouTube logo on top right.
Click on a song to play and below the songs look for “add to” button and click on playlist name that you have created as I have created a playlist “My favorite Songs” and that songs will be added to your playlist. Here is an option to create another playlist.

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