Complex sentence: As a child Thomas Pinto played the violin well, and aged 11 he could play the concertos of Arcangelo Corelli; he was leading important concerts before he was twenty.
Split into simpler sentences: As a child Thomas Pinto played the violin well, and aged 11 he could play the concertos of Arcangelo Corelli. Because of his noted ability, he was leading important concerts before he was twenty.