Consonant, consistent, compatible, congruous, congenial, sympathetic are comparable when they mean being in agreement one with another or agreeable one to the other.
Consonant implies agreement with a concurrent circumstance or situation, or conformity to an accepted standard, or harmony between two things that must come into contact or comparison with each other; the term suggests absence of discord.
Consistent suggests such agreement or harmony between things or between the details of the same thing as implies the absence or avoidance of contradiction.
Compatible implies a capacity for existing or coming together without disagreement, discord, or disharmony; the term does not necessarily suggest positive agreement or harmony, but it does imply the absence of such conflict between two or more things as would make their association or combination impossible or incongruous.
Congruous implies more positive agreement or harmony than compatible does; ordinarily it implies the fitness, suitability, or appropriateness of one thing to another so that their association or combination, no matter how much they are in contrast, produces a pleasing or at least a not disagreeable impression.
The negative form incongruous is currently far more common than congruous.
Congenial is most often used of persons or things that are in such harmony with the taste of a person that they afford him pleasure or delight or satisfaction.
Occasionally congenial is used of things in the sense of wholly and satisfyingly congruous.
Sympathetic (see also TENDER), like congenial, usually suggests qualities in the person or thing so described that make him or it in agreement with another person's likings or tastes, but, in contrast with congenial, it suggests a more subtle appeal and often a less hearty acceptance.