There are many ways that a triad can be voiced into a four-voice texture. In the first example, the C triad is simply undergoing a shift of position, with different notes of the triad being distributed to the various upper voices. Since the C remains in the bass, these chords remain in root position.
In the next example, however, the bass line also receives a distrubution of notes, such that the bass sometimes has the 3rd or 5th of the chord. We say then that chord has been inverted. The manner of this inversion is simple:
If a chord has the root in the bass, the chord is in root position.
If a chord has the third in the bass, the chord is in first inversion.
If a chord has the fifth in the bass, the chord is in second inversion.
If the chord is a seventh chord, as in the case of a dominant seventh, and the seventh is in the bass, the chord is in third inversion. We will discuss seventh chords soon.
The above is true, regardless of how the rest of the voices are distributed. As long as the third is in the bass, for example, then the chord is in first inversion. The upper voices can then be voiced in a variety of ways.
We can indicate these in a simple manner by putting the number of the chord tone below the Roman numeral. So a first inversion tonic chord can be indicated with a 3 below the Roman numeral I, to indicate that the third is in the bass, but the chord itself is still the tonic triad. The 5 below the I indicates that the fifth is in the bass, but the chord is still a tonic triad.
The same can then apply to all other harmonies. If you look back at the harmonic analysis of Lo, How a Rose e'er Blooming, you will notice the indications of the chord inversions below some of the ii, iii and V chords.
There is another method for indicating chord inversions, which is based on the procedure of figured bass. This is method most commonly in use among practicing music theoretians and will be covered in the next section of this chapter. I want you to understand the basic concept of inversion before moving into the topic of figured bass notation.
Chord Inversions using Figured Bass symbols.
The system in the above section used a simple notation to indicate inversion: a '3' below the Roman numeral if the triad were in first inversion (with the third in the bass), and a '5' below the Roman numeral if the triad were in second inversion (with the fifth in the bass).
However, this is not the system that is currently in practice. The symbols that are actually used combine Roman numeral chord notation with the system of figured bass, creating a hybrid symbology that shows both function and inversion.
This might be a good moment to go back and review the chapter on figured bass, as it related to our work with three-part counterpoint.
Figured Bass for Harmonic Triads in root position and inversions
Having reviewed figured bass, we can then look at how the Arabic numbers from the figured bass are combined with the Roman numerals to show both chord inversion (the Arabic numbers) and chord function (the Roman numerals).
You can know quickly learn these short hands for root position chords and inversions. You will use them both for realizing harmonic progressions in four parts and for providing harmonic analyses for musical passages and compositions.
Root position—no figure
First inversion—Roman numeral with a 6 superscript
Second inversion—Roman numeral with a 6 superscript and 4 subscript.
FIgured Bass for Dominant Seventh Chords, root position and inversions
Seventh Chords are a bit more complex, for the simple reason that they are four-note sonorities: a harmonic triad upon which is added the seventh above the root.
Let's focus for the moment on the dominant seventh chord in the key of C, which is the G7 chord, that is: a G major triad with a minor seventh above the G (the F natural).
This chord can and is voiced with any of the four notes in the bass. From that bass note, we can take the figures from figured bass procedures and add those figures (or in some cases, a shorthand version), to produce the following:
Root Position—has just a 7 (1-3-5 implied)
First Inversion—the intervals above the bass is 3-5-6, which is abbreviated to 6-5.
Second Inversion—the intervals above the bass is 3-4-6, which is abbreviated to 4-3.
Third Inversion—the intervals above the bass is 2-4-6, which is abbreviated to 2.
Note the shorthand: 7, 6-5, 4-3, 2 for root position, first inversion, second inversion, third inversion, respectively. This is an easy pattern to rembmer, because if simply descends:
Root position: 7
First inversion: 6-5 (with the third in the bass)
Second inversion: 4-3 (with the fifth in the bass)
Third inversion: 2 (with the seventh in the bass)
Here's how the root position and inversion chords might flow in a simple chord progression played at the piano, with the bass notes in the left hand and the chords voiced in the right hand.