IV. Diatonic Harmony, Tonicization, and Modulation

John Peterson

Key Takeaways

This chapter discusses the various ways in which composers harmonize la $(\hat6)$ in the bass depending on where it’s found within a phrase: beginning, middle, or ending.

• At phrase beginnings, la $(\hat6)$ is often used to prolong tonic in two ways:
• harmonized with IV6 in the progression $\mathrm{I-IV^6-V^6_5-I}$ (Examples 1 and 3)
• harmonized with plagal (IV6) in the progression $\mathrm{I-IV^6-I^6}$ (Examples 2 and 4)
• At phrase middles, la $(\hat6)$ is often used:
• in a deceptive motion (V(7)–vi) (Examples 5 and 7)
• to connect the tonic (T) and strong predominant (PD) areas, harmonized with vi (Examples 6 and 8)
• At phrase endings, la $(\hat6)$ is often used:
• to create a (iv6–V in minor) (Examples 7 and 9)
• as a “stand-in” for the expected strong PD note fa $(\hat4)$ (Example 10)

# Overview: uses of la (scale degree 6)

So far, we’ve seen every scale degree appear in the bass except for la $(\hat6)$. In this chapter, we see that la $(\hat6)$ is commonly harmonized by two chords: vi or IV6. It may show up in beginnings, middles, or endings of phrases, and each location is associated with particular progressions that involve la $(\hat6)$ in the bass.

# At phrase beginnings

When la $(\hat6)$ appears in the bass at the beginning of a phrase, it typically prolongs tonic in one of two ways: (1) using IV6 as a predominant in the progression $\mathrm{I-IV^6-V^6_5-I}$ (Example 1), or (2) using plagal (IV6) in the progression $\mathrm{I-IV^6-I^6}$ (Example 2).

Example 1. Tonic prolongation via $\mathit{I-IV^6-V^6_5-I}$ in Josephine Lang, Arie.

Example 2. Tonic prolongation via $\mathit{I-IV^6-I^6}$ in Josephine Lang, Lied.

## Using IV6 as a predominant

Writing $\mathrm{I-IV^6-V^6_5-I}$ can be tricky, particularly when $\mathrm{IV^6}$ goes to $\mathrm{V^6}$, since there is a danger both of parallels and of a doubled leading tone. No single piece of advice can guarantee that you’ll avoid problems. When you write $\mathrm{I-IV^6-V^6_5-I}$, the soprano lines do–do–re–do $(\hat1-\hat1-\hat2-\hat1)$ and mi–mi–fa–mi $(\hat3-\hat3-\hat4-\hat3)$ will help, but you’ll need to check carefully for parallels. Using $\mathrm{V^6_5}$ instead of $\mathrm{V^6}$ will also mitigate some of the danger of parallels (Example 3). Note that this progression doesn’t work well in minor, where the bass would create an augmented second from le to ti $(\downarrow\hat6-\uparrow\hat7)$. The rare occurrences of this progression in minor raise le to la $(\downarrow\hat6$ to $\uparrow\hat6)$ to avoid the augmented second (Examples 3c and 3d).

Example 3. Writing with $\mathit{I-IV^6-V^6_5-I}$.

## Using plagal (IV6)

Writing $\mathrm{I-IV^6-I^6}$ is relatively easy (Example 4). Here, remember three things:

1. The bass always arpeggiates down.
2. The most common soprano is mifasol $(\hat3-\hat4-\hat5)$.
3. The other voices should move by step or common tone.

Example 4. Writing with plagal (IV6).

# At phrase middles

In the middle of a phrase, la $(\hat6)$ shows up in the bass in one of two ways:

1. To avoid a cadence as part of a deceptive motion (Example 5)
2. To connect the tonic area to the strong predominant area by arpeggiating dolafa $(\hat1-\hat6-\hat4)$, harmonized by vi or IV6 (Example 6)

Example 5. Deceptive motion in Bernhard Henrik Crussell, Clarinet Quartet Op. 7, II, mm. 66–72 (5:06-5:38).

Example 6. vi connecting T and strong PD areas in Bernhard Henrik Crussell, Clarinet Quartet Op. 7, II, mm. 1–4 (0:00-0:18).

## Deceptive motion

When a V chord sets up the expectation for a cadence, but moves instead to an unexpected, non-tonic harmony, this is called . Deceptive motion most commonly occurs when V(7) moves to vi rather than I, with the bass moving solla $(\hat5-\hat6)$. Less commonly, la $(\hat6)$ may be harmonized with IV6 rather than vi in a deceptive motion. Writing deceptive motion with V(7)–vi carries an inherent danger of parallels that can be avoided by doing the following two things (Example 7): (1) resolve tido $(\hat7-\hat1)$ as you would do normally, and (2) move all upper voices in contrary motion to the bass (downward).

Example 7. Writing deceptive motion.

Some people use the term “deceptive cadence” to describe what we refer to as “deceptive motion.” Since the progression V(7)–vi avoids a cadence rather than creating one, we find that the term “deceptive cadence” inaccurately describes the progression’s purpose, so we prefer the more neutral description “deceptive motion.”

## vi as a weak predominant

Using vi to connect the tonic and strong predominant areas is quite easy to write (Example 8). As long as your upper voices move by step or common tone and you follow , you should not run into writing issues. Notice that for the phrase model analysis (T/PD/D) labels, the PD label goes on the first strong PD before the cadence, as in Example 6.

Example 8. Writing with la $\mathit{(\hat6)}$ connecting T to strong PD area.

# At phrase endings

La $(\hat6)$ may appear at the end of a phrase in one of two ways:

1. As part of a phrygian half cadence (Example 9)
2. Harmonized with a predominant chord as part of a push to a cadence

Example 9. Phrygian half cadence in Franz Schubert, “Die Mainacht,” mm. 1–10 (0:00-0:19).

## The phrygian half cadence (PHC)

The is a special kind of cadential phrase ending that occurs only in minor and involves the progression iv6–V. It’s called “phrygian” because of the half step that occurs when le moves to sol $(\downarrow\hat6-\hat5)$ in the bass, a sound that’s similar to when ra moves to do $(\downarrow\hat2-\hat1)$ in the . The progression carries a danger of parallels and of writing an augmented second between le and ti $(\downarrow\hat6-\uparrow\hat7)$. These can be avoided if you choose to double do $(\hat1)$ in the iv6 chord (Example 10). Very often, PHCs are approached from i, and are accompanied by the soprano me–fa–sol $(\hat3-\hat4-\hat5)$, as in Example 10.

Example 10. Writing a PHC.

## La $(\hat6)$ harmonized with a predominant at a cadence

It’s possible to see la $(\hat6)$ harmonized with a predominant (usually vi or IV6) at a cadence without the presence of fa $(\hat4)$ in the bass before the cadential dominant (Example 11). This is much less common, however, than seeing fa $(\hat4)$ in the bass harmonized with a strong predominant before the cadence.

Example 11. La $\mathit{(\hat6)}$ as “stand-in” for strong PD in Joseph Haydn, String Quartet Op. 76, no. 2, I, mm. 1–4 (0:00-0:08).

Assignments
1. La $(\hat6)$ in the bass at beginnings, middles, and endings (.pdf, .docx). Asks students to analyze bass lines, write from figures and Roman numerals, harmonize an unfigured bass, and analyze an excerpt.