@nyev I noticed that when I listen to classical, especially Piano or Violin (any E concerto), the sound is a bit bright in the 4fs mode. I change to original (the NOS mode is called original in Grimm) and the slight tinge of brightness is gone. The NOS mode sounds amazing in these types of music. This may also be due of my system. The quality of recordings also plays a role. So it’s not universally bright with these types of music.
Any acoustic music (think jazz) sounds phenomenal in 4fs mode. In fact, at the risk of sounding hyperbolic, I would say that if Jazz is your primary genre of choice, Grimm with 4fs is outstanding and I cannot imagine anything regardless of price sounding better.