Growing up in China, Xian Zhang had no idea that female conductors were rare birds; two of her mentors were women. Her rise since moving to the United States two decades ago has been steady rather than meteoric. Her résumé is looking seriously classy now, and so are her reviews. A nice alignment of the planets brings her to London for Mahler’s sublime symphonic song cycle Das Lied von der Erde (The Song of the Earth), which is anchored in Chinese poetry and shot through with Chinese imagery. Andreas Schager takes the athletic heldentenor part; Dame Sarah Connolly is heard in the contemplative, supremely moving movements for mezzo. Two cases of ideal casting. —M.G.