Alan Yentob investigates the extraordinary impact music can have on the human brain. He travels to meet Tony Cicoria, who was struck by lightning and suddenly developed an insatiable passion for the piano, and Matt Giordano, who can alleviate his severe Tourette's syndrome by drumming - both remarkable case studies from neurologist Dr Oliver Sacks's latest book, Musicophilia. Alan even has his own brain scanned - with surprising results.