Sibelius was influenced by the natural world around him, and his Fifth is evocative of the grandeur and isolation of his native Finland.A formation of 16 swans flying overhead even inspired his sweeping “swan hymn.” Tonight at 7:30 at Mandel Concert Hall, the Cleveland Orchestra will perform the piece along with selections from Walton and Ades. Performances continue through Saturday. Consult the orchestra's website for more info.