undersong

The devils' tattoo on the roof had sunk to a mere undersong, a fitting accompaniment as it were to the electricity in the room.

Undersong, un′dėr-song, n. the burden or chorus of a song: an underlying meaning.

The afternoon was past its height, but bright yet, with the undersong of the wind and of Thunder Run.

Beneath the chorus of their hearts' joy there was an undersong of discord; and neither knew of the other's perplexity.

It called the support of The Examiner “the sweet undersong of the weekly journal.”