[McAroni]

You could. I would do this with filters to select and identify your files. In the filters search for compser or genre in the corresponding fields you used, or click on the down arrow and Search there by the fild you want to edit.  For the polkas for instance. If there are more then one entrys i would put all the filtered songs into a temporary Setlist. Now select all songs in the new created Setlist and click Batch Edit. Then you could batch Edit all the entrys you want. After that you could delete the Setlist...

The same you could do direct in MSP