Possible Clues:

• "America, the Beautiful" pronoun
• "Of ___ I sing" 1931 musical
• "Get ___ behind me . . ."
• What makes us use you?
• Friend's addressee, maybe
• Pronoun in hymns
• The key for you, historically
• You once had resistance leaving trio
• Bruce Springsteen and ___ Street Band
• ". . . 'tis of ___"