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What would be the reasons for composers to write notes with the same letter name (eg C) an octave apart and have one in root position and the second one in first inversion. For example, the first C will be middle C in root position and the second C in first inversion an octave apart.

Any specific reason for writing the chords this way? If yes, what would be the functions of these 2 chords? Do these chords normally resolve to certain chords?

Thank you all for the contributions. I'd like to share the following to explain what I mean because I think I made a mistake with one of the chords. This is ABRSM G7 model answers for its Q1 chord notation question.

I've seen a few composers write in this manner - first chord C in root position (CEG) followed by A in first inversion - (CAE) with the C in the bass written an octave apart from the C of the previous chord and then followed by D#. Are there any reasons for writing the harmony this way? Thanks.

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  • Welcome! There’s a little confusion here. Is the question really “why would people use first inversion chords?“ Note, an inversion just tells you which note is in the bass. A first inversion C chord could have the C two octaves higher, or four, or missing entirely! Nov 4, 2023 at 16:37
  • @AndyBonner - not sure how an inversion of a C chord could be missing a C note.
    – Tim
    Nov 4, 2023 at 17:07
  • first inversion means taking the third chord factor and using it as the bass (lowest) note in voicing. Could you give an example? image of the score or how it is written? Maybe you mean something else, I don't think it's possible to write a C as a first inversion of a C chord. @AndyBonner I don't think you can omit the C from a C chord? if you inverted a C chord and didn't play the C then it would be a different chord? I'm confused haha
    – yarns
    Nov 5, 2023 at 20:10
  • Is this question about notes or chords? Nov 6, 2023 at 2:28
  • Perhaps your question is really focused on octave leaps in the bass? This excerpt contains a lot. In the measure you drew a square around, one is root position and one is 1st inversion, but that's kind of just a coincidence of which chords were needed. Nov 6, 2023 at 14:56

4 Answers 4

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Octaves are equivalent harmonically but not equal. The octave above a given note has twice the frequency; when sounded together, there's not much difference in tone.

However if sounded with a different note, there is a difference. The interval C to E is a major third; the interval from this E to the C above is a minor sixth; they do not sound the same. Either interval can be the constituent of a C-major chord. We could also add a G above the E and compare the sounds of C-E-G with E-G-C. These are both C-major chords; they do not sound the same. They have the same root, C, but the arrangement of notes is different.

When composing a harmony (or improvising one, the same thing but occurring more quickly), there are two "progressions" that one must be aware of. They are both important. The movement of chordal roots (called the harmonic progression) matters (or at least for a plurality of music from the 1500s to today) is audible; it is often used structurally to signal phrases or sections of music and to create feelings of movement, repose, or finality.

The other "progression" is the succession of the lowest notes. This is the bass line; in root position chords, the bass note coincides with the chordal root. (Statistically, this occurs for about 70% of the chords, according to a few articles I have read.) When all chords are in root position, the music can tend to become stagnant (boring). When the third of a chord (E in a C major chord) is in the bass, the chord sounds different but functions similarly.

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  • Thank you very much for responding to my question. Much appreciated! Apologies for not making the question clearer....
    – user95334
    Nov 9, 2023 at 16:15
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I'm guessing - just that, the question means why use different inversions of a particular (here C) chord in their playing/works.

With C at the bottom, it's a root position, and sounds very solid and grounded. In 2nd inversion, it still sounds pretty solid, whereas in 1st inversion, a little unstable. But that actually works in its favour if the next chord is root F, as the bass leads up from E to F. One reason it's called a leading note, in this example, not of key C but key F. So voicing can play a big part in which inversion gets used.

It's also dependant on what the melody may be - some inversions work better than others. Also using root with every chord change can get pretty tedious to listen to. There's also the fact that a bass instrument may be looking after the root, so on piano or guitar, it gives the opportunity to vary what would otherwise be a boring (quoting ttw) accompaniment.

Of course, this may be not what the question is asking, in which case, forgive me, and make it a tad clearer!

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  • Thank you very much for the feedback! Much appreciated! Apologies for not making the question clearer.
    – user95334
    Nov 9, 2023 at 16:13
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I've seen a few composers write in this manner - first chord C in root position (CEG) followed by A in first inversion - (CAE) with the C in the bass written an octave apart from the C of the previous chord and then followed by D#. Are there any reasons for writing the harmony this way?

First, those are C♯s and G♯s, not Cs and Gs. Also note that the chord changes on the third beat, so the D♯ is the bass of a first-inversion B major chord, D♯-F♯-B.

But to answer your question, at the time this music was written the modern theory of inversions was in its infancy and had been rejected by many of the composers who were active when it was first published, J. S. Bach among them. The driving force in this music is melody and counterpoint. Harmony is definitely present, of course, but the reason for writing the piece this way is that the composer wanted a bass line that falls an octave and then moves up a whole step and then a half step.

(Looking at the bigger picture, the bass line is characterized by repetition of a small number of three-beat patterns at various pitch levels, and one of the patterns comprises three quarter notes ascending by step. The octave drop is necessary to keep the bass part in the desired range; had the A in the bass been an octave lower, the C♯ would most likely have been repeated in the same octave instead.)

A common way to harmonize stepwise motion in the bass line was known as the "rule of the octave." This "rule" is more of a guideline, and you can find several variants of it. It allows the composer or continuo player to avoid the parallel fifths that would result if every bass note were to be harmonized in root position. Typically most of the chords are 6 chords, which in the descending version are often decorated with 7-6 suspensions. In the ascending version, the analogous approach yields a sequence of alternating 5/3 and 6/3 chords, or, in modern terminology, alternating chords in root position and first inversion.

In this case it's not even clear that the given figuration is correct, as the A and G♯ in the first beat are both arguably ornamental; you could argue for either one being the "true" chord tone there.

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  • Thank you very much! This is the answer that I was looking for. Much appreciated for the corrections and the answers. Apologies to everyone for not making the question clearer in the first place.
    – user95334
    Nov 9, 2023 at 16:10
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When playing a chord, the note at the top tends to me more prominent. So in a triad in C, C-E-G, the G is more readily heard than the C or E. If the chord is inverted, then C becomes the top note, and dominates. (For that reason, if I intend to end a piece on a chord, I will often choose the first inversion of the tonic.)

There's another pragmatic reason to use inversions - to keep the accompaniment and melody a suitable distance apart. If the accompaniment drifts too high, it crashes into the melody and you end up trying to play the same notes in both hands at the same time. If the accompaniment drifts too low, it sounds muddy. You can find that one triad crashes into the melody, while a triad an octave below sounds bad. In that case, a solution is to switch to an inversion of the chord to find a nice place between those two. (You can also cheat and use one of the notes in the melody to complete a chord in the accompaniment. For example, if you decide that a G needs a C chord, play the C and E only in one hand, and the G from the melody completes the chord.)

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  • "If the chord is inverted, then C becomes the top note, and dominates": Inversion is determined only by the bass note. The top note can be C in any inversion. (In three voices, however, in root position, then either the third or the fifth must be omitted for both the bass and top voice to have C. But three-voice part writing typically has many incomplete chords.)
    – phoog
    Nov 6, 2023 at 10:22
  • For example, the first movement of Beethoven's Moonlight Sonata ends with a root position C-sharp minor chord with C sharp as the highest pitch, and the final chord of Bach's mass in B minor is a D-major chord in root position with the highest pitch being a D.
    – phoog
    Nov 6, 2023 at 10:48
  • The 3rd sentence is slightly misleading. Cleared up partially in the 4th, but could be more clear. Probably the reason for dv.
    – Tim
    Nov 9, 2023 at 16:17

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