Well drum parts are drum parts. And you can cut up loops into pieces and re-assemble them. ALL loops started off as intended to be part of a piece of music. Loops can be organized as a collection of themed loops (e.g., drum loop library, acoustic guitar strums library, etc.) or as construction kits. Either way, you have a collection of individual loops.
It's too bad I was fired before getting a chance to finish the next Tech+Music, which had an article covering how to use loops in general. However it will appear in one of my upcoming Sound on Sound columns.