Possible Clues:

• "Hello Muddah, Hello Fadduh" singer Sherman
• Poe’s middle name
• Mystery writer's middle name
• Adventurer Quartermain
• Jazz guitarist Holdsworth
• 'Haggard' described his wife
• Singer Sherman
• The 'A' in E. A. Poe
• "King Solomon's Mines" hero Quatermain
• The A of E.A.P