Harmonize

v.calm, joyfulprofessional

Meaning 1

To bring different people, rules, or parts into workable agreement.

Reach for it when describing deliberate alignment that preserves useful differences

The partners will harmonize their safety rules before sharing the site.

warm
blend
different elements should combine softly into a whole
not when Blending can erase individual character that harmonizing allows to remain audible.
professional
align
goals, rules, or actions need to point in the same direction
not when Alignment can enforce uniformity, while harmonizing may keep distinct parts intact.
professional
coordinate
timing and responsibilities must work together efficiently
not when Coordination can succeed without shared principles or genuine agreement.
formal
reconcile
an apparent conflict between positions or accounts must be resolved
not when Reconcile focuses on incompatibility and can sound too serious for minor coordination.

To sing or play notes that combine pleasingly with a melody.

Reach for it when talking about adding compatible musical parts

By the second chorus, the audience began to harmonize with the trio.

playful
vocalize
making sung sounds matters more than their musical relation
not when Vocalize names sound production without assuring that the notes complement the melody.
everyday
sing together
the plain fact of shared singing is enough
not when Singing together may be in unison rather than in complementary notes.
formal
accompany
one musical part supports a featured voice or instrument
not when Accompaniment can be rhythmic or identical and need not harmonize.

harmonize standards
Regional offices agreed to harmonize standards for accessible signs.
harmonize with
The new brick must harmonize with the weathered stone.
voices harmonize
Their voices harmonize most clearly in the quiet final verse.

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