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victoria Williams Music Theory

Victoria Williams

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3. Creating a Simple Trio Sonata

Grade 8 Music Theory - Creating a Simple Trio Sonata

The secret to writing a part which sounds like a trio-sonata part, is to focus primarily on the melody notes which fall on the main beat of each bar, and to treat these notes as a “main melody”.

Any notes which are squashed between these important notes can be thought of as melodic decoration. In a piece written in 4/4, for example, the main melodic line will often be made from the four notes which fall on each crotchet (quarter note) or minim (half note) beat.

  • When creating the “main melody”, the basic idea is that a melodic line moves smoothly. For the most part, it will move by step to the next note, and when it cannot move by step it will move by a 3rd.
  • At cadences, a rise of a 4th or fall of a 5th are common, and they are also sometimes used elsewhere in the melody for short periods.
  • Leaps of a 7th are rare.
  • Augmented and diminished intervals are treated with care.
  • Each note of the “main melody” will normally correspond with a change of chord in the harmony.


We’ll use this Trio Sonata by Telemann (TWV 42 in A minor) as an example. At first sight, the top part looks very busy (the middle part is silent here), but we can boil it down to something more simple, by looking at the notes which fall on the beat. Notes which are categorised as “melodic decoration” have been greyed out. What is left, is what I call the “main melody”.

creating trio sonata outline 


In bar 1, the first two beats of the bar fit with an A minor tonic chord. We will treat the quavers (8th notes) E-A-C as melodic decoration: they are harmonic auxiliary notes (i.e. chord notes which are ornamental, and not important in themselves).

In the second half of bar 1, the harmony changes to a dominant E major chord, with B falling on the strong beat. (Remember that in quadruple time, the 3rd beat of the bar is the second strongest). This E major chord actually lasts until half way through bar 2, where the 7th, D is also added, before the harmony changes back to A minor. In bar 1, the quaver (8th note) E, and the following semiquavers (16th notes) can be considered as decoration of the B. The E and G# are harmonic auxiliary notes, and the F# and A are passing notes.

In the first half of bar 2, E-B-D are harmonic auxiliary notes.  In the second half of bar 2, the tied D is a suspension, which resolves to the true harmony note, C. The quick notes are decorative – harmonic auxiliary notes and normal auxiliary notes - and they don’t make the melody move away from the A minor harmony.

In bar 3, the first note in the bar is B, which forms part of chord ii° (B dim).

On beat 2, there is a leap of a diminished 5th to F, and the harmony here is a German augmented 6th chord (chord notes F-A-C-D#). Having the main melody leap by a dissonant interval is not recommended – instead we can treat the F as decorative, and consider the A to be the main melody note.

The third beat of bar 3 only uses G#, so this must be part of the main melody.

This leaves us with a very simple “main melody”.

creating trio sonata main melody 

When it comes to writing your own parts, it’s a great idea to begin with a simple “main melody” like this, and then work some melodic decoration into the gaps between each “long” note. This way, you will ensure that your melody sounds plausible, rather than (perhaps) a random succession of “notes which fit the harmony”!

The kind of melodic decorations which are squeezed in are the usual suspects:

  • Passing notes
  • Auxiliary notes
  • Harmonic auxiliary notes
  • Suspensions
  • Anticipations
  • Retardations
  • Changing notes

Of all these types, the first three are the most commonly used. Personally I think that changing notes are the hardest to use effectively, and are probably best avoided unless you have a very good inner ear and plenty of aural experience to guide you.


Creating the Main Melodies

Let’s work backwards now, to create two main melodies to fit a bass line, and then decorate them in a Baroque style.

This is the bass line we’ll use. I think it helps to pencil in the letter names of the chords before you start, so you can more quickly understand which notes you can choose from to make the melody. For the same reason, you can also write in the letter names of any notes which will need to appear in suspensions too.

 creating trio sonata bass line

We’ll start by adding one part, and then add the other (rather than working vertically, chord by chord).

I’ll write in a main melody for the top part, with one note falling on each chord change. In this case there are four beats per bar, but the harmony is changing with each half bar, so we could write a main melody with crotchets (quarter notes) and/or minims (half notes).

With each note you write in the first part, make sure that:

  • You haven’t doubled the third of a root position major chord (in a minor chord it’s acceptable, but usually there is a better option).
  • You haven’t doubled the leading note in the prevailing key. (Notice any key changes, however short-lived. In this case, the piece starts in C major, but by the end of bar 2 has moved to A minor, meaning that G# is the leading note at this precise point).
  • You haven’t created consecutive perfect 5ths/8ves with the bass line (check with the bass note which is directly above the figure AND with any melodic decoration notes in the bass, so in bar 1, you need to check against the first C, and then check again against the E which follows).
  • You don’t move in similar motion 3rds/6ths with the bass for more than two bars (it gets tiresome on the ear, and the independence of parts becomes lost as they meld together).
  • Aim to move mostly by step or 3rds. For variety, add a limited number of 4ths, 5ths or octaves.
  • Use different types of motion with the bass line: use contrary motion as well as similar motion.
  • Try to avoid two jumps in the same direction (i.e. thirds or greater)

If the note you choose means that there is, as yet, no root, third or required suspension in the chord, write a reminder, on the middle part stave, of the note that will be added at that point, for the chord to be complete. (5ths can be omitted, except in a 6-4 chord or diminished chord).

creating trio sonata top part 

After checking carefully for consecutives, add in the middle part. When adding this last part you should:

  • Check for consecutive 5ths/8ves with the top part AND bass line (separately).
  • Don’t double the third unless it’s a first inversion chord, or a minor chord, and never double the leading note in the prevailing key.
  • Aim to make most chords “complete”, i.e. with a root, third and fifth.
  • As with the top part, move mostly by steps and thirds, but also add 4ths/5ths/octaves for variety.
  • Don’t forget that the top and middle parts can cross each other.
  • Don’t let all three parts move in similar motion.
  • Make sure you added in the “reminder” notes!

To fill in this middle part, I’ll begin on G, the note which is missing from the C major triad.

 creating trio sonata middle part

Now we need to add in melodic decoration to liven it up. I’ll be using semiquavers (16th notes), and try to split them between the two parts, so that there is a degree of balance. The decoration will mostly be a combination of auxiliary harmony notes, passing notes and normal auxiliary notes. Ties can be used liberally. Always look for opportunities to create sequences. Notice how the two upper parts rarely have an identical rhythm at the same time, and there is a slight slowing down (less use of semiquavers (16th notes)) as we approach the end of the phrase.

 creating trio sonata decoration 1

creating trio sonata decoration 2


The result is something which sounds plausibly Baroque! (The recording here uses flute and oboe for the upper two parts.)





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