Part-writing Chords: Mediant and Submediant I
The mediant and sub-mediant chords—triads built upon the third and sixth scale degrees, respectively—are less frequently used than the triads previously considered in this series of Hubs. (This is especially true of the mediant.) It’s partly for this reason that these two chords can be used to broaden and freshen harmonic color.
Before looking at some normal uses of these two triads, though, the reader may wish to check whether it would be helpful to work through some of the previous Hubs in this series—the knowledge contained in them is assumed in the rest of this Hub. Below are lists of the topics that are covered in each of the preceding Hubs.
- Part-writing Chords: Tonic And Dominant I
How to write the most common Classical chord progression, with audio/video examples and easy-to-understand explanations.
Part-writing Hub #1
- Lead sheet
- “Spacing” of voices
- Parallel and contrary motion of voices
- Concept of “voice leading”
- “Root position,” “voicing,” and “line”
- Polarized roles of tonic and dominant chords in Classical harmony
- Resolution of “leading tone”
- “Open” versus “close” chord spacing
- Chordal “doubling”
- “Common tone”
- Part-Writing Chords: Tonic And Dominant I (Exercises)
A companion to "Part-Writing Chords: Tonic And Dominant I"--practical exercises to build skill in part-writing tonic and dominant chord connections.
Part-writing Hub #2
- Vocal ranges
- Rule for determining sharp keys from key signature
- Rule for determining flat keys from key signature
- Chords with missing thirds
- Part-writing Chords: Subdominant I
Third in a series, this Hub examines the use of the subdominant chord--the "IV chord"--in traditional ("common-practice") harmony, with practice exercises.
Part-writing Hub #3
- Root motion by fifth
- Root motion by second
- Parallel motion [perfect or imperfect intervals]
- Similar motion; similar fifths and octaves
- Incomplete triads [omitted fifths]
- Tripled root voicing
- Part-writing Chords: Supertonic I
Learn to use the 'ii' chord in true Classical style with essential concepts, practice exercises, and audio-video examples.
Part-writing Hub #4
- Primary and secondary triads
- “Doc Snow rule of doubling”—better known in association with Walter Piston!
- “Hybrid spacing”
- IV normally precedes ii in Classical style
- Chord substitution
- Deceptive cadence
- Voice overlap
- Grand Staff Templates | Free Blank Sheet Music
Free blank grand staff templates in portrait and landscape orientation in PDF format.
If any of this seems unfamiliar or confusing, it would probably be best to spend some time working through (or at least reviewing) the relevant material.
As always, I strongly suggest answering the questions physically, on actual music manuscript paper, as you proceed through this Hub. As usual, I’m providing a link to free manuscript paper that you can print out.
In the previous Hub we considered the concept of chord substitution, noting that since third-related diatonic triads—as, for example, ii and IV—share two of three chord members, they will thereby exhibit some sonic similarity. Supertonic and subdominant—ii and IV—are especially vivid examples of this tendency, since in normal usage both chord tend to lead to a dominant triad—the “V” chord. That is what music theorists mean when they say that both ii and IV “function” as preparations for the dominant.
(In fact, this notion of chordal “function” is widespread and influential; theorists recognize chords of all sorts as possessing “tonic,” “dominant” and “dominant preparation” “functions.” But that is a discussion for a later Hub.)
First, let’s look at the mediant and submediant in the context of the major scale:
As shown, the mediant is the iii chord. Its name seems to recognize the fact that its root lies midway between tonic and dominant in the scale:
Correspondingly, the submediant, vi, has a root lying midway between that of the tonic and the subdominant.
The mediant and submediant can also be placed in a more specifically harmonic context, though. We noted in the last Hub how tonally strong, and how common, the progressions ii-V-I can be. This is so because of the powerfully stabilizing root motion by fifth it exemplifies:
This motion can be further extended ‘backwards’ to incorporate the submediant and mediant chord, too:
Notice the striking sound of the mediant—but also the purposeful flow of the harmony, dominated as it is by the tonally strong root motion by descending fifth. These harmonies seem to drive toward the tonic with great energy and purpose, moving systematically from the most 'distant' diatonic chord, the mediant, to the tonic.
Notice, too, that the second and third chords—iii and vi—form a unit that is replicated down one scale step by the fourth and fifth chords—ii and V. This type of transposed repetition is termed a ‘sequence’ and it’s a useful musical technique.
Let’s try writing variations of that progression. Identify the key and scale degrees in the soprano below:
It’s in Ab, and the scale degrees in the soprano are 5-5-6-4-5-3.
Using the example above as a model, add a bass line.
Now add alto and tenor voices in turn.
Here’s another twist on the same chord progression. Name the key and scale degrees in the soprano below. Also, which of the lines in the previous question does this soprano resemble?
The key is D major, the scale degrees are 1-7-1-6-7-1, and the line is very close to the tenor line in the preceding question; only the last note is changed. Why does that last note need to change?
While you ponder that, add a bass line.
You may have thought that the line needs to change because the C# at the end of the first full measure is the leading tone, and when ‘exposed’ in the soprano or bass, instead of ‘hidden’ in the alto or tenor, it needs to resolve to the tonic. If so—congratulations! That’s exactly right.
Now add alto and tenor.
Another harmonic context for vi and iii occurs when, rather than appearing ‘as themselves’ in a ‘falling fifths’ progression like those we have just been examining, the mediant or submediant appears as a substitute for some other chord.
Which substitutions are possible? That is, which triads are a third away from (and therefore share two tones with) the mediant and submediant? The answers will be obvious to some readers, and perhaps puzzling for others. If you are not one of the first group, don’t give up right away. Write out on paper the lower two notes and the upper two notes of the vi chord:
Now do the same for the iii chord. For each pair of notes, there will be one tone which will form a ‘new’ triad. Work through the four possibilities. You should end up with something very similar to this:
Ex. 7Click thumbnail to view full-size
So, vi can potentially substitute for I—as mentioned in the last Hub of this series, this commonly happens in the context of the “Deceptive Cadence”—or for IV. It isn’t hard to find examples of vi leading to V, which could be thought of as vi substituting for IV, although it isn’t usually viewed in that way.
The mediant triad, similarly, could substitute for either I or V. If you think about it, that is a remarkable thing, since, in the context of Classical practice, tonic and dominant functions form the opposite poles of tonal harmony. Possibly this very ambiguity helps explain why one sees relatively few examples of the iii triad. Yet there are usages which suggest precisely these mediant substitutions, as we’ll see.
Beginning with the submediant, here are two versions of the progression I-vi-V-I. As mentioned a moment ago, one way to think of this would be that the vi chord substitutes for the IV chord we would expect to lead to V. Like the IV chord, vi has a potential pitfall when leading to V: since the root motion is by second, objectionable parallel fifths or octaves could easily arise. This danger must be avoided by making sure that the upper voices—or at least those involving root and fifth of the V chord—must move in contrary motion to the bass. Here are two examples:
In the first version, the inner voices, which contain the root and fifth, move contrary to the bass. The soprano moves in parallel thirds with the bass. In the second, all three upper voices move contrary to the bass; this is the more common version, and allows smoother motion in the upper voices.
Try this progression in another key. As usual, start by identifying key and scale degrees. To which voice—and which version—of Example 7 does the given soprano correspond?
The 3-3-5-3 soprano in F major corresponds to the 3-3-5-3 alto in Example 7b, so use that example as a model to help you add bass, alto and tenor voices.
Let’s try the “deceptive cadence” progression, in which vi substitutes for I. I’ll throw you in at the deep end by first giving a version using the subdominant: I-IV-V-vi. (The obvious alternative, I-ii-V-vi, would not fit with the soprano’s “G.”)
The problem that this creates is that you now have two successive root motions by second; each requires careful use of contrary motion with the bass in order to avoid troublesome parallel perfect intervals. See if you can navigate this challenge successfully; identify key and scale degrees, then add the appropriate bass.
As you can see, the soprano and bass move in contrary motion only for the first of the two motions by second, moving instead in parallel thirds for the V-vi progression. Add alto, then tenor.
Now let’s try a version using the ii chord. This soprano could be harmonized with either ii or IV, but we’ll avoid the double motion by second we saw in the last question. However, as you consider your bass line, be careful—this melody poses other pitfalls. See if you can avoid them.
This bass line is forced by the downward skip in the soprano from the “A” to the “F#,” because a downward leap in the bass—“F#” to “B”—would create objectionable similar fifths. Therefore, the bass must leap upward to the “B” instead—and that means that it must start low in order to avoid ‘squeezing’ the inner voices at the end of the progression.
Once the bass line is correct, though, writing the inner parts is fairly easy. Write alto first, then tenor—either order works fine in general, but the alto is given first below!
Q5c-dClick thumbnail to view full-size
The alto and tenor must move contrary to the bass in the I-ii, as always. The doubled “A” in the ii chord is normal—remember the “Doc Snow doubling rule” that the primary tones within a key are the first choices to be doubled!
Unfortunately, that doubling also means we can’t keep a common tone when moving from the ii to the V—but the resulting tenor is doubly OK, even though it arrives by similar motion at an octave to the bass. First, that ‘similar octave’ does not involve two outer voices, which it must in order to be a problem. Second, it is approached by step in the tenor, and to be a problem it must be approached by skip or leap in the soprano.
You may have written a “C#” in the alto for the very last chord. This is not the worst mistake ever, but the “E” is a better choice, since “E” is the primary tone found in the triad. The “Doc Snow doubling rule” strikes again!
Let’s try some examples (arguably) involving mediant substitutions, too. Here’s an example in which iii can be seen as substituting for I: I-iii-IV-V-I. Once again, this involves consecutive root motions by second. As usual, contrary motion between upper voices and bass prevents problems.
Note the descending scale in the soprano, and how the leading tone is harmonized by the iii. The leading tone normally ‘wants’ to resolve upward, especially when placed in an outer voice. But you do find descending scale segments like this one—and often it is the iii triad which is chosen to harmonize the leading tone instead of the more usual V chord. (This tends to ‘soften’ the leading tone’s characteristic tendency.) From this perspective, you might think that the iii is really substituting for V, not I—but remember that V-IV is a very rare progression in Classical harmonic style; I-IV is much more ‘plausible.’
Try this progression in another key. Identify that key and the soprano scale degrees as usual.
It’s F#, and the scale degrees are (of course!) 1-7-6-5-5—it’s the same soprano. Adding bass and inner voices should be no problem.
Here’s another variation on the theme: ii can substitute for IV in the preceding progression. Harmonize this soprano with I-iii-ii-V-I.
We’ll conclude with a couple of progressions which don’t so clearly reflect the concept of substitution. First is a straightforward progression using root movement by fifth. What are the key and scale degrees of the soprano below?
The line is 1-1-6-7-1, in the key of Bb. Harmonize it with the progression I-vi-ii-V-I.
Now consider this soprano:
Although it is in Bb, like Question 8, the “Bb” on beat 3 means that using a iii chord there is unworkable, as the chord does not contain that tone. So, an extra credit question, not too hard: what other chord might you use on beat 3?
If (after a suitable pause for thought) you reasoned that ii and IV are frequent substitutes for one another, that the Bb would form the fifth of a IV chord, and that therefore the harmonization might well be I-vi-IV-V-I—well, then congratulations: “Good work!”
Now complete the harmonization in our usual manner.
This progression is quite common in many styles. It can readily be found in Classical repertoire, and was a favored set of ‘changes’ for a great many doo-wop hits from the 50s and early 60s—in fact, in that context, the progression deserves the label of “cliché”. Here’s an invented (but very typical) example:
Let’s finish this Hub with an “exam question,” a longer, tougher challenge. Here’s the soprano:
It’s in D, as you can probably readily see by now. How could one go about harmonizing this?
It’s designed to allow you to use the examples already given in this Hub. Notice, to begin with, that the first measure closely follows the pattern of Example 10 (repeated here so you don’t have to scroll back up to look at it.)
So the harmonization would closely reflect what was done in that example.
What about measure 2? Well, first I’m going to mandate that beat 1 be a vi chord, forming an example of the “deceptive cadence” progression, as shown in Questions 4 and 5 above. (It’s an unusual example, admittedly—usually the soprano in a deceptive cadence is either 7-1 or 2-1.)
Further—for reasons too lengthy to go into here—we don’t want to use another vi chord on beat 2 of measure 2—in fact, we don’t want to repeat the same chord consecutively in these exercises at all. So what chord should we use on beat 2?
Let me put forward as model a progression discussed in PW Hub #4:
The progression is I-IV-ii-V-I. Notice the sequence IV-ii in particular: as we have discussed, these chords can substitute for each other, but they can also occur in succession. In Classical practice, though, the sequence is usually IV-ii, not the reverse, since the ii triad tends to 'drive' toward the dominant chord more strongly.
Can you use this to advantage in the question we are working on? (Hint, hint!)
So, with models to apply, can you figure out the chords to use which will let you write a bass line for that soprano? I’ll give the answer in two phases. (You may or may not need to be walked through the process in detail, so I would suggest that you try working out the answer on your own. Then—and only if needed—you can refer to the following explanation.)
First, the chords. For measure 1, applying the model suggested would give a I-iii-IV-V chord progression. For measure 2, vi was given on beat 1, harmonizing scale degree 3. We can be sure that a V chord is required to harmonize the scale degree 7, on beat 4 of measure 2, and that we will end with a I chord.
So our problem comes down to two chords—those found on beats 2 and 3. We need to get from vi to V. What two chords connect those two? Well, the example given as a hint above contains the sequence IV-ii-V. Can we logically move from vi to IV? Of course! We just did so, in our “doo-wop cliché” example, after all. So measures 2-3 can be harmonized vi-IV-ii-V-I.
Second is the challenge of writing the actual bass line. In this key, there’s an obvious choice of octave for the beginning tone, and if we follow the model it will dictate our tones up to the first beat of measure 2. (That’s one of the advantages of thinking linearly, as we have been doing in this series of Hubs.)
In the second measure, it will be best to keep to the same general register as the first measure, even though there are some possible tones in a lower part of the bass range. These will not sound as good, though, because they will force one or more of several things best avoided: we could 1) jump more than an octave; 2) leap or skip several times in the same direction; and we could 3) outline a dissonant interval. All of these are both subtly grating to the ear, and harder to sing than the alternative.
Putting all these considerations together gives us the bass line below. (If you already got it, then—again!—“Good work!” If not, well, this was meant to be a challenge, so don’t feel discouraged.) Now add alto and tenor parts:
Q10b-dClick thumbnail to view full-size
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And that’s it! Here ends the first part of our consideration of part-writing. We’ve looked at how to part-write all major-key diatonic triads in root position, examining normal harmonic patterns and the pitfalls they may sometimes contain.
Compulsive score-keepers may notice that we haven’t looked at the viio triad yet—that’s because it is not normally used in root position! (We will consider it when we deal with triads in inversion.)
Others will notice that minor key usage still needs to be dealt with as well. That will be the topic of the next Hub in this series.
Other Hubs by Doc Snow
- Part-writing Chords: Summary I
A 'syllabus' and summary for Doc Snow's innovative Hubs on the essential musical skill of part-writing. Sequence, content and links--plus a summary of part-writing 'rules.'
- Part-writing Inverted Chords: Primary Triads In First Inversion
How to use inverted triads in common-practice four-part writing. Learn to write tonic, dominant and subdominant in first inversion--these explanations, illustrations, and practice examples make it easy!
- How (Not) To Practice Music Efficiently, Part One
The first of a pair of articles on how (not) to practice music, this article sets the record straight on much confusing practice advice you hear. Plus, great pictures of some musical greats!
- Better Faster: Top Ten Music Practice Tips
"Practice, practice, practice!"--But what about practicing *smarter*? This article gives ten useful tips to do just that. Get better, faster!
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