Ternary has three main keys for example ABA so if you had a song yoy would repeat it so...
A- the dog slept on the coach
B- the cat meowed
A-the dog slept on the coach
so as you see you repeat what you say not all tye time do so for a song with Aba is "Twinkle,Twinkle little star how i wonder what you are, like a dimond in the sky , twinkle , twinkle little star."
so they repeat twinkle twinkle little star in the song.