Mellow

adj.calm, joyfuleveryday

Meaning 1

Pleasantly gentle, relaxed, and free from sharpness.

Reach for it when describing a mood, person, light, or atmosphere with easy warmth

A mellow mood settled over the group after the long meal.

playful
laid-back
for distinctly informal praise of an unhurried style
not when Its casual register clashes with dignified or professional description.
everyday
relaxed
when lack of tension is the main quality
not when Relaxed can mean careless or informal without mellow warmth.
warm
easygoing
for a person or atmosphere that accepts change without fuss
not when Easygoing can imply weak standards and does not suit color or light.
warm
gentle
when softness in manner or effect matters
not when Gentle can be quiet and careful without the seasoned ease of mellow.
literary
serene
when calm appears clear and untroubled
not when Serene is more elevated and lacks mellow's casual warmth.

Rich and smooth in sound, color, or flavor.

Reach for it when praising sensory character that has softened or deepened

The cello held a mellow tone even in its lowest register.

everyday
smooth
when harsh edges or rough transitions are absent
not when Smooth can be bland and does not imply depth.
everyday
soft
when low intensity or gentle texture is the exact feature
not when Soft can lack richness and may imply weakness.
warm
rich
when fullness and depth in sound, color, or flavor are central
not when Rich may be intense or heavy rather than soft.
professional
rounded
when sound or flavor feels full without sharpness
not when Rounded fits sensory balance but not a person's mood.
professional
warm-toned
when sensory color or timbre should be described precisely
not when The phrase is technical and misses relaxed emotional character.

The definition and the example on this page are written here. The dictionaries above ground which meaning is being described, not the wording.