Possible Clues:

• Pop music middle name that can be spelled two ways
• Opera 'Moses und ___'
• Schönberg opera 'Moses und ___'
• Elvis follower?
• Rock-'n'-roll middle name
• Middle name of 67 Across
• Middle name of 'the King'
• Schoenberg's "Moses und __"
• Middle name of "The King"
• Cal's "East of Eden" brother