That's a thorny question. What Willingham really wants here is a #sampling license - a license that allows licensees to take *some* of the elements of his work, combine them with other parts, and make something new.
But no CC license fits that description. Every CC license applies to *whole* works. If you want to license the bass-line from your song but not the melody, you have to release the bass-line separately and put a CC license on *that*.
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