Plot: From an icy Italian winter to the heady, sensual warmth of a South American summer: violinist Joshua Bell leads the Academy of St Martin in the Fields on a musical journey through the sights and sounds of two continents and four very different seasons. Inspired by Vivaldi’s best-known work, Piazzolla – Argentina’s 20th-century tango king, whose 100th anniversary we celebrate this year – created his own response, complete with musical quotations