What are iii/III chords used for in classical music?

[ranjit]

What are the possible ways in which the chord built upon the third scale degree is used in classical music? The only thing I can think of is the circle of fifths progression.

In addition, what function does it serve? e.g., in the major key, ii and IV are subdominants, V and vii° are dominants. Functionally speaking, what is the meaning of the iii chord?

[rachmaninoff_forever]

It can be used for pretty much anything.

Modulation, substitutions,, passing chord, maybe it just sounds pretty, you name it.

[visitor]

+1 @ rAch4Ever

short : add /build tension. It's tonally unstable in the scope of the tonic

and like R4e mentioned, very handy as for either outright modulation or temporary forays into false modulation territory, in  minor mode, it very much works as a V of VI0, which allows a piece in c minor to move into key of b flat major with almost seamlessly.

[themeandvariation]

from a major scale standpoint - the iii Can function as a substitute for the V - (if one wants to draw parallels with the ii and IV relation)… it can also act as a v of Vi…
The III - from the standpoint of a major scale , is the V of Vi.

[klavieronin]

You also see it a lot in harmonic sequences.

[ranjit]

It can be used for pretty much anything.

Modulation, substitutions,, passing chord, maybe it just sounds pretty, you name it.

+1 @ rAch4Ever
and like R4e mentioned, very handy as for either outright modulation or temporary forays into false modulation territory, in  minor mode, it very much works as a V of V, which allows a piece in c minor to move into key of b flat major with almost seamlessly.

Thanks for the reply, but can you or someone else on this forum please provide some examples of these? -- it would be much clearer to me that way. What is false modulation? It is not obvious to me how the iii/III can be used as a substitution, or as a passing chord. What would the iii/III substitute for?

Also, you can modulate from the iii/III chord, using it as a V of V chord, but how do you reach the chord in the first place?

[visitor]

Thanks for the reply, but can you or someone else on this forum please provide some examples of these? -- it would be much clearer to me that way. What is false modulation? It is not obvious to me how the iii/III can be used as a substitution, or as a passing chord. What would the iii/III substitute for?

Also, you can modulate from the iii/III chord, using it as a V of V chord, but how do you reach the chord in the first place?

you need.to.buy or check out a theory textbook, basic music school theory course stuff wil .address it I don't have mine around  here but will see if I can find it

[brogers70]

My textbook on tonal harmony lists the following normative uses of the III/iii chord (the mediant)

iii in the Major

1. iii to vi as the start of a circle of fifths progression -> iii to vi to ii to V to I

2. iii directly to ii or IV

III in the minor

3. III to VI as the start of a circle of fifths as above

4. III directly to iv or iio

Apart from these, III in a major key is the dominant of the relative minor, and can be used to modulate to the relative minor.

And apart from these uses as chords, you can think of the mediant as a possible key in larger forms. Beethoven liked to use the mediant key as an alternative to the dominant in sonata form. So where in an earlier sonata form the second theme group in the exposition would typically be in the dominant (or the relative major if the movement was in a minor key) Beethoven would have the second theme group in the mediant. In a multi-movement piece Beethoven would often have a slow movement in the mediant key (even Haydn did this sometimes - one of the late Haydn piano sonatas in C major has a slow movement in E major).

I'm sure there are additional uses for the mediant, but this is a start.

[visitor]

see attached very basic disc and helpful diagram I used a ton from my tonal harmony text 4th ed.

[ranjit]

Thanks visitor, brogers70. This was very helpful.

Yes, I think I need to buy a music theory textbook to learn these things.

[reynolduk]

You will better off understanding from 1st principles. Reference and study from a book: Alfred’s Basic Music Library: Scales, Chords, Arpeggios and Cadence. This way you will understand better the question you phrased here. Circle of fifths and Circle of fourths is where your question lies. The answer lies if you narrow down your question as it is a technical matter in music theory. There are 12 major scales and 12 relative Minor scales to each major scale. For example C major, relative to C Major is the A Minor scale. Each major scale is made up of 2 tetrachords: C,D,E,F and G,A,B,C. 8 notes in a set of C major. This also applies for all remaining major scales. G, D, A, E, B, F#, C#, F, Bb, Eb, Ab, DB, Gb, and Cb Major.. Each time you understand this concept. C Major being 8 notes. The root is C, it is also referred to as the I chord. It is also called a Tonic from the perspective of notes by degree ( steps ). So, if your understand  circle of fifths and what make up the major scales: there are 12 inclusive. Hence there are that many variation of 12 of I chords, or tonics, etc. That’s circle of Fifths (clockwise) and another 12 ( anti-clockwise ). The lowercase Roman numerals refers to the position of the notes of Minor scales. Your question what are iii/III chords used for in classic music is 12 Major scales and 12 Minor scales. The Minor scales is further broken down into Natural, Harmonic and Melodic. So this is your answer when you ask and I narrow it down to this answer. You need to learn these concepts as they are distinct and musically technical. It matters when you want a roadmap to direct your music playing. It’s hard to understand it but playing it and applying it to your piano exercises you build up your muscle memory, aural memory, and sight-reading skills. In Classic music the chord is mentioned which Major key the music it is in. You get an equivalent in relative Minor scale. They are used for referencing finger work positions of a major or Minor scale. Techniques like inversion referencing the same but Major scales is uppercase Roman numerals, lowercase for relative Minor to Major scales. You have a set of labels to name each degree position of notes. An octave. Tonic To Tonic. Then each note within an Octave is as follows: Tonic, SuperTonic, Mediant, subdominant, dominant, sub median, leading tone and Tonic. It’s is hard to remember the name set in the notes of Octaves. It is given another set of names and numbered using Roman numerals. Hence for Major scale. It is Tonic (I), supertonic (II), mediant (III), subdominant (IV), dominant (V), submedian (VI), leading note (VII) and Tonic (I). A scale is a set of musical notes. An Octave is a set of 8 notes. A Scale is an Octave. Tonic is not a scale. III chord is 3 music notes stacked one on top of the other on the Stave ledger ( music sheet ). A chord is not a scale. A chord is a reference to the scale it is within. With Major or relative Minor.  You play it together, striking all 3 notes together. You an also strike it one by one within the time signature to give you arpeggios of the chord. Broken chord. For example, You can express the chord as staccato or Legato for arpeggios. This concept does not just apply to classical music. It applies to Music. Take your time to understand this grounding of music theory. It helps you to read into music. It helps you to compose, transpose, transcribe music. There are other styles of playing piano, jazz, blues, etc. The scales and chord will be your reference point. There will be more of the same but musically and technically different to apply and reference. For example scales and modes. Main modes are: Ionian(C), Aeolian(A), Dorian(D), Phrygian(E), Lydian(F) Mixolydian(G).