SMT Nocturne is probably my favorite OST
https://www.youtube.com/watch?v=OM-MMOCZlZg
https://www.youtube.com/watch?v=H5EAhOnt4N8
https://www.youtube.com/watch?v=A54JyDE8jsg&list=RDOM-MMOCZlZg
https://www.youtube.com/watch?v=M2qZB9UQ-Iw