Possible Clues:

• Frankie of the Four Seasons
• Four Seasons leader
• Singer Frankie
• The 4 Seasons frontman Frankie
• "My Eyes Adored You" singer
• 'Grease' singer
• “Sherry” singer
• Role in the 2005 hit musical 'Jersey Boys'
• 1960's-70's vocalist known for his falsetto
• 'Rag Doll' singer, 1964