“A few decades ago, I would not have put money on the survival of the concerto, except as an antiquarian curiosity. Celebrity soloists continued milking the classics, but the rest of the music world seemed to have moved on from all that gladiatorial bravura.” Justin Davidson looks at four new concertos – by Sofia Gubaidulina, Lera Auerbach, Esa-Pekka Salonen, and Timo Andres.