I had this same problem when new to clip and it drove me crazy. I finally found I had to get mp3tag, a free program, and learn to tag or change tags in the music. Cant just rename them for they are electronically tagged and apparently that is what the clip sees. If I rip in media plaer i can edit tags ther or use mp3tag afterward, but if i get music elsewhere then I have to use mp3tag to change tag. Sometimes you can just type the tag as you want it; other times you must remove existing tag or what you type wont stay. I like to make artist folders named for artist first and last name, then put songs in them retaining the track number in title and below in the track box. This way I can trace the song back to an album if i wish. In the clip they arrange according to track number, but then I am not interested in keeping albums separate although i could, nor am I interested in other details like year, genre, etc. Because I simply want all the music by a single artist in one folder and to just listen.
To accomplish the tagging I open mp3tag, drag the artist album to window and the song tracks appear. I click Edit> Select All. Then I choose KEEP in the title box if OK, and type the Artist name in both the artist AND album boxes for I only want to deal with Artist folders, even though the clip will aso show them as albums. I find it confusing to have albums different than artists, although others may not and may choose that method.
After typing what whant, you must not click anything else but go right up to bar and click the Save Tag icon and OK when saved tag box appears. If click something else before saving , what you typed will likely disappear and you have to do it over.If song already has has tag you must go to drop down menus and find Remove Tag, and click it after selecting desired song(s). If want to keep any existing components then choose ‘keep’ in that box.If remove tag and dont keep you may have to retype things.
I hope this helps. I was completely new to all this and learned to use it by just working with it, making mistakes, and getting better. knew nothing of mp3 players before getting my first Clip 5 months ago and learned all by trial and error and this forum. (Thank you Forum - couldnt have done it alone).
So to get rid of Unknowns you should get mp3tag, learn to remove and change tags to what you want.
If I have made no mistakes in my attempt at explanation you should achieve the “No Unknown” goal. Good Luck.