Replete with emotion, color, energy and intimacy, the Portsmouth Symphony Orchestra opens its 25th season with Gustav Mahler’s Symphony No. 5 and George Walker’s Lyric for Strings. Mahler’s giant work traces the emotional pathway from funeral march to radiant optimism while Walker’s brief but deeply intimate work is dedicated to his grandmother, a former enslaved person who died while Walker was composing the piece. Seemingly opposites in size and origins, these two profound works mirror one another in their capacity to convey the complexity and intensity of the human experience.