It is the last of September’s searing heatwave, and we are in Peckham Rye’s cafe, looking out onto the arid stretch of grass, sipping iced coffee and fresh lemonade appreciatively. The Odyssey Festival Orchestra (OFO) has been rehearsing for a couple of weeks now for its forthcoming Astonish Me! concert, and I am here to get to know its leader, Leon Human, who is entering his final undergraduate year at the Guildhall School of Music and Drama.