Ahnornberg’s “no return” manages an unusual combination. It bears the lightness of classic ambient music — to be distinguished from classical ambient music, which might be taken to mean ambient music with a classical-music affect, like the work of Mary Lattimore, Christina Vantzou, or Nils Frahm — even as its tonality veers into darker territory. Dark ambient is also often dense ambient. That coloration is heard here, especially in its closing minutes, but even so it never loses the fragility of the earlier portions. What does disappear is the misty figment of a melody that initially wafts through.