The phrase "subtle spirit" is correct and usable in written English.
You can use it to refer to someone or something that is characterized by quiet strength or subtle influence, such as a gentle breeze or an unassuming leader. For example, "She had a subtle spirit that made her a natural leader."
The order's ritual prayers (dhikr) are based upon thousands of repetitions of seven names of God, identified with seven "subtle spirits" (laṭāʾif sabʿah) which in turn correspond to seven lights.
If one were to identify a divine counterpart for the screenwriter Joe Eszterhas it would have to be Hephaestus, the volcanic wonder-worker of Olympus, whom my encyclopaedia describes as a "robust smith [read: wordsmith] with bearded face, powerful neck and hairy chest" under whose "graceless exterior, however, lurked a subtle and inventive spirit".
Since strong-flavored spirits take longer to pick up the more subtle vanilla flavor, the bottles need to be shaken so that the vanilla gets distributed.
Subtle Midwinter of the Spirit is not, and it loses some genuine scariness because of it.
But it is good to remember that war can vex the spirit in subtle and unexpected ways.
But there may be subtle changes in the spirit if not the essential purposes of the holiday, just as there have been changes in the demography of the marchers.
We were pleased that the commentators observed those things -- many people overlook these important but subtle communications, in the spirit of "Pay no attention to the man behind the curtain".
In the abstract, we use the term "minimal" for the role of PPC, which seems close in spirit to "subtle".
Even softly played, yet "hard" music can have a subtle effect on the spirit, for better or worse; which many or most people are, or seem to be, more or less oblivious to.
