Pianist Leif Ove Andsnes describes the unique qualities of Rachmaninoff's Piano Concerto No. 4, Andris Nelsons talks about Shostakovich's music for King Lear and Mahler's Symphony No. 4, and Marcus Thompson, Peggy Pearson, and Dimitri Murrath of the Boston Chamber Music Society talk with WCRB's Cathy Fuller about works by Bax and Bliss.