The dc:source property can denote an upstream source (the track that was remixed). The cc:derivativeWork property can denote a remix of a track. ccMixter uses only the former. Skipping verbose rdf/xml syntax with complete URIs, we have something like
cc:Work about="" cc:license by-nc-sa dc:source example.com/somework
cc:License about="by-nc-sa" permits ...
cc:Work about="example.com/somework" cc:license ...
Unless the reused work is public domain attribution must be provided for works reused in a manner consistent with other attribution for the medium, e.g., listed on the work's web page as done at ccMixter. In a video reused works might be listed in credits --  which uses CC licensed music and images in their videos provides an example of this.
When metadata is colocated with human readable content both the machine- and human-readbale information tend to be more accurate and better maintained. (forthcoming)
"Who remixed me?" as the new "Who linked me?"