field with multiple foreign keys I have researched this on my own but not really sure of the terms I should use and have not gotten far.  Basically I'm trying to figure out how to implements tags for a table row.  So if my table was musicFile, my tags would be artist, genre, etc....  But lets say some musicFiles would only have artist, or genre so its variable.  

I think I would need a separate table for Tags but even then there would have to be foreign keys that are placed in the musicFile table and I end up at the starting point since its 1-1, meaning that its still variable.  I would not know at database creation time how many fields to dedicate to Tag foreign keys.
If a MusicFile has multiple Artists and an Artist has multiple MusicFiles then yes you need a link table between the two (as per the answer in your comment). However, if, for example, you only ever want to attach a single Genre to any given MusicFile, then you could just have a field for genre inside the MusicFile table.