Another pair of words whose distinct meanings have been blurred by carelessness. The problem centers on masterful, in such phrases as a masterful artist or a masterful performance. Make it masterly, which means "highly accomplished," "inspired," "demonstrating mastery."
Masterful has darker shadings. It's about being the alpha dog: dominant, supreme—almost ruthlessly so. A masterful performance should refer to a boxer or a victorious football team rather than a cello concert.