in a minor key

in a minor key

Having a subtle, understated presentation or demeanor. An allusion to the musical key, the phrase is typically used to describe abstract concepts and characteristics. The film, which elegantly examines the very real struggles of everyday people in the modern age, is human wisdom in the minor key.
See also: key, minor

in a minor key

(especially of a literary work) understated.
1995 Independent He was a moralist in a minor key.
See also: key, minor
References in classic literature ?
Following on the Odes, we have much written in the same style, more often than not by women, or songs possibly written to be sung by them, always in a minor key, fraught with sadness, yet full of quiet resignation and pathos.