code: def _to_chroma(pianoroll):
      
      _validate_pianoroll(pianoroll)
      reshaped = pianoroll[:, :120].reshape(-1, 12, 10)
      reshaped[..., :8] += pianoroll[:, 120:].reshape(-1, 1, 8)
      return np.sum(reshaped, 1)
docs: Return the unnormalized chroma features of a pianoroll.