Possible Clues:

• 'Barber of Seville' composer
• Composer of 'The Barber of Seville'
• Composer of 'The Barber of Seville' and 'William Tell'
• He composed a piece of music - 'The Hero's Sin' in C
• Composer-violinist's treatment captivates southern Italy
• Composer of The Thieving Magpie
• Largo al factotum composer
• ''The Thieving Magpie'' composer
• Whom the French called ''Monsieur Crescendo''
• His barber was 25, he noted ...