In music theory, each chord within a key plays a specific role that creates a sense of stability, movement, and tension within a progression. These chord functions fall into three primary categories: tonic, subdominant, and dominant. Understanding these core functions—and the flow from one to another—is essential for creating progressions that feel cohesive and dynamic.

This central framework—moving from tonic to subdominant to dominant and back to tonic—is one of the most fundamental concepts in music. This progression provides a natural cycle of movement that feels satisfying to the ear. Let’s dive deeper into each function and examine how they interact in both major and minor keys.

Tonic, Subdominant, and Dominant Defined

At its core, the tonic is the “home base” or the most stable chord within a key, providing a sense of rest and resolution. The subdominant acts as a transitional chord, moving the harmony away from the tonic, while the dominant chord creates tension that resolves back to the tonic. Each of these chords has its own unique qualities, defined by their intervals.

1. Tonic Chords (I, III, and VI): Tonic chords can include a 7th but not a 4th. For instance, in C major, Cmaj7 works as a tonic chord because it includes the notes C, E, G, and B—no 4th, but a 7th is present. This “no 4th” quality helps create a stable, restful sound without the tension that would come from a subdominant or dominant chord.
2. Subdominant Chords (II and IV): Subdominants include the 4th scale degree but avoid the 7th. For example, in C major, Fmaj7 acts as a subdominant because it contains F (4), A, C, and E but no B (the 7th). This structure creates movement, stepping away from the tonic without building up the tension that calls for resolution.
3. Dominant Chords (V and VII): Dominants include both the 4th and the 7th, creating the highest level of tension and a strong pull back to the tonic. In C major, G7 is a classic dominant chord, containing G, B (7th), D, and F (4th). This “4 and 7” combination makes dominants the perfect setup for returning to the stability of the tonic.

The Tonic → Subdominant → Dominant → Tonic Flow

The natural flow from tonic to subdominant to dominant to tonic is at the heart of nearly every progression. This cycle is both logical and satisfying, creating a seamless sense of movement. Here’s why each transition works:

• Tonic to Subdominant: Starting on a tonic and moving to a subdominant creates a sense of departure from the stability of home.
• Subdominant to Dominant: The subdominant transitions toward the dominant, setting up tension that builds anticipation.
• Dominant to Tonic: The dominant chord’s tension releases as it resolves to the tonic, completing the cycle.

This movement is universal, and you can start at any point within this cycle for an equally satisfying progression. For example, moving from F (subdominant) to G (dominant) to Am (tonic) works well in C major, following the same tonic–subdominant–dominant–tonic pattern.

Examples of the Core Cycle in Action

To illustrate this formula, here are some example progressions that follow the Tonic → Subdominant → Dominant → Tonic cycle:

• Example 1 (Key of C Major): | Am (VI) | F (IV) | G (V) | C (I) |
• Example 2 (Key of Am): | E7 (V) | Am (I) | Dm (IV) | Am (I) |
• Example 3 (Key of G): | G (I) | C (IV) | D7 (V) | G (I) |

Each of these progressions follows the natural cycle of movement, establishing a solid foundation for the listener. The final resolution to the tonic chord feels especially satisfying because of the gradual buildup of movement and tension.

Reversing the Flow for Added Interest

While the natural order from tonic to subdominant to dominant works well, sometimes reversing this flow can add intrigue to a progression. For instance, going from dominant to subdominant can create a fresh twist in the music. However, it’s best to resume the natural flow afterward to maintain coherence within the piece.

Here’s an example progression in the key of D that incorporates a reversal:

| A (V) | D (I) | G (IV) | A (V) | Em (II) | A (V) | D (I) |

Notice how moving from A (dominant) to Em (subdominant) creates a momentary reversal, yet returning to the tonic afterward brings back the familiar cycle, enhancing the listener’s experience.

Tonic as a Flexible Interjection

One of the unique qualities of tonic chords is their ability to appear almost anywhere in a progression without disrupting the flow. Inserting a tonic chord within a progression creates moments of stability, allowing other chords to build movement and tension around it.

For example, here’s a progression in C minor that demonstrates how the tonic can be interspersed:

| Cm (I) | Fm (IV) | Cm (I) | G7 (V) | | Cm (I) | Dm7b5 (II) | Gm (VI) | Bb (VII) |

The second Cm chord doesn’t disrupt the flow; it simply adds a temporary resting point. The third Cm chord, by contrast, is part of the natural progression from G7 (dominant) to Cm (tonic) to Dm7b5 (subdominant), reinforcing the flow.

Applying the Concepts in Minor Keys

The tonic–subdominant–dominant cycle also applies to minor keys but with some adjustments. In minor, we often borrow from the harmonic minor scale to create a stronger pull back to the tonic.

For instance:

• Tonic (I, III, VI): In a minor key, these remain the tonic chords, but the intervals reflect the minor quality. For instance, in A minor, Am7 (I), Cmaj7 (III), and Fmaj7 (VI) serve as the tonic chords.
• Subdominant (II, IV): In A minor, the subdominants could be Bdim7 (II) or Dm7 (IV), reflecting the minor key’s qualities.
• Dominant (V7, VII): The harmonic minor introduces a raised 7th to strengthen the dominant pull. For instance, in A minor, E7 acts as a dominant with G# as the raised 7th, creating a strong resolution back to Am.

The dominant-to-tonic resolution in minor is particularly powerful when using the harmonic minor scale, as the raised 7th note pulls the harmony back to the tonic.

Practical Tips

1. Understand the Role of Each Chord Type: Recognize the unique intervals of each chord type to understand the tension or stability they bring.
2. Follow the Tonic → Subdominant → Dominant → Tonic Cycle: This natural flow creates a sense of direction in any progression.
3. Use Reversals Sparingly: While reversing the flow can add interest, make sure to return to the natural cycle to keep the progression coherent.
4. Interject the Tonic Anywhere: The tonic can be placed almost anywhere within a progression for stability, without disrupting the natural flow.

Mastering Progressions Through Functional Harmony

Understanding tonic, subdominant, and dominant functions—and how to create a satisfying progression through tonic, subdominant, dominant, and back to tonic—can enhance any musician’s grasp of harmony. By following this fundamental cycle, experimenting with reversals, and recognizing when to insert the tonic for stability, you’ll unlock new layers of creativity and depth in your music.