Cantion is a rarely used word, and it may not have many synonyms. However, some words that may have similar meanings include chant, song, hymn, or melody. Each of these words is related to music and could be used in place of cantion in certain contexts. For example, instead of saying "I love the sound of this cantion," you could say "I love listening to this hymn." Additionally, some words like composition, tune, or piece could also be used interchangeably with cantion to describe a musical work. Although cantion may not have many synonyms, there are several words that could substitute for it depending on the context in which it is used.