undertone

An auditory tone of low pitch or volume.

An implicit message perceived subtly alongside, but not detracting noticeably from, the explicit message conveyed in or by a book, film, verbal dialogue or similar (contrast with overtone); an undercurrent.

A pale colour, or one seen underneath another colour.

A low state of the physical faculties.

To accompany as an undertone.

To say or speak in an undertone.

To present as less important, noticeable or prominent.