A musical structure where the piece is divided into 3 distinct sections. The 1st and last sections are exactly the same as each other and so the form can be written A – B – A as below:
Each of the sections sound like complete pieces of music in themselves – you could play just the A Section of a Ternary Form piece and it would not “feel” like it must continue onto a new section. This is because it ends on a perfect/authentic cadence.
The B Section is usually written in a key that is closely related to the key of the A Section as below:
The B section also usually has a different mood to the A Section. If the A Section is upbeat and lively then the B Section will often be more subdued.
Have a look/listen to this famous example of Ternary Form – “Alla Hornpipe” by Handel from The Water Music.
Compound Ternary Form
This is when each of the sections (A-B-A) are subdivided into a clear Ternary Form structure as in the diagram below. Examples of Compound Ternary Form include trios and minuets.
Composing in Ternary Form
Ternary Form is a great structure to compose in because the repeated A Section gives your piece a sense of unity and balance which you don’t quite get in Binary Form. The contrasting B section will also help focus you to create fresh ideas and bring variety to your composition.
I would suggest writing an A Section (you may have already written a piece of music that would work well as an A Section in a Ternary Form piece).
Once you have finished your A Section try writing a new section, but use the different keys suggested in the Ternary Form diagram above.