1. to combine or blend in a pleasing or consistent way; to make compatible or in agreement
Usage: British spelling (American: harmonizes); third person singular present tense
2. to add harmony to a melody; to arrange or compose musical parts that blend with a main tune
Usage: music; British spelling (American: harmonizes); third person singular present tense

Examples

• The new policy harmonises workplace rules across all departments.
• Her calm demeanor harmonises well with the peaceful atmosphere of the library.
• The composer harmonises the violin melody with rich string accompaniment.
• These colors harmonise beautifully in the interior design.
• The team harmonises their efforts to meet the project deadline.
• She harmonises the lead vocal with a soft background part.