Admixture

A mixture

Something mixed with something else

Air being a physical substance is an admixture of several gases

he felt that his work was an admixture of aggression and creativity

leucocholy

though it seldom laughs or dances, nor ever amounts to what one calls joy or pleasure, yet is a good easy sort of a state

Or
a preoccupation with trivial or unimportant matters

Or

Opposite of melancholy

He had many leucocholy reflections of his old school days.