vibraphone:
  (quant 200)
  (key-signature "f+ c+ g+")
  a8 b > c d e f g a <
  a b > c_ d e f_ g_ a <

  (key-signature [:g :minor])
  g a b > c+ d e f+ g <

  (key-signature {:e [:flat] :b [:flat]})
  g1~1/b/d