 As in an oratorio , the written text in a choral symphony can be as important as the music , and the chorus and soloists can participate equally with the instruments in the exposition and development of musical ideas . The text can also help determine whether the composer follows symphonic form strictly , as in the case of Rachmaninoff , Britten and Shostakovich , or whether they expand symphonic form , as in the case of Berlioz , Mahler and Havergal Brian . Sometimes the choice of text has led the composer to different symphonic structures , as with Szymanowski , Schnittke and , again , Havergal Brian . The composer can also choose to treat the text fluidly , in a manner more like music than narrative . Such was the case with Vaughan Williams , Mahler and Philip Glass . 
