concealed
hidden octaves
invisible
unseeable
abstract
abstruse
arcane
beclouded
behind the curtain
behind the scenes
between the lines
blind
buried
cabalistic
camouflaged
censored
classified
close
closed
clouded
covered
covert
cryptic
dark
deep
delitescent
disguised
dormant
eclipsed
enigmatic
esoteric
guarded
hermetic
hibernating
hid
hush-hush
imperceptible
in a cloud
in a fog
in eclipse
in purdah
in the wings
incommunicado
indiscernible
insensible
latent
lurking
muffled
mysterious
mystic
obfuscated
forbidden
glidden
overridden
ridden