I believe enhancements were made that allow queries over relationships to just use the foreign key value rather than force a table join, but I am not sure of what version this was put in - you may have to use TopLink 12/EclipseLink. You should move to a later version if possible anyway, as I do not know how long TopLink 10.1.3 is supported for.
That said, as long as there is a join to Singer, both Singer and Artist tables will be pulled in. If you cannot upgrade to a version that can optimize out the join, the best way forward is to add a query key for the ARTISTID foreign key in Song and any other descriptors that may reference the Artist table. Query keys act just like basic mappings without requiring an attribute in your object. More information and examples can be found following the links from here: