An antonym is a word that has a meaning opposite or contrary to another. Example: The antonym of light is dark, good is bad, etc. Sonata is a musical composition for one or two instruments structured in three or four movements, or times. I do not think that there is something contrary to a sonata, unless it is the cantata, which is sung with voices instead of touched with instruments. This is rather different but not the opposite.
In music there are many forms and genres, according to the time of the composition, the instruments used, the use of the human voice or not, its religious nature or not, their melodic or rhythmic features. So is not the same a Chaconne, a flight, a night, a parade, a rondo, a Symphony, an overture, a sonata, a madrigal, a motet, a cantata, a madrigal or a Christmas Carol. They are different musical compositions, but they are not considered antonyms together but different. The sonata can be very different from the cantata because the first involves one or more musical instruments but never the human voice, what happens if in the cantata.
