Harmonic Functions

5. Cycling Functions

Cycling TDS is the core mechanism of building a “story” with chord progressions. The mood produced by shifting functions can be explained like below:

In LMT, rotating the inner cycle (T–S–D–T) is termed Prograding Motion, while the outer cycle (T–D–S–T) is termed Retrograding Motion.

Prograding the Cycle

The reason why we call T–S–D–T rotation “prograding” is that it follows the theory of tension & release; it accumulates musical tension gradually, then release it in one go, which is expected to bring the sense of fulfillment to listeners.

Imagine it like riding a roller coaster. The stronger tension is accumulated, the stronger satisfaction you’ll get when it’s released. This tension-release system is true of other entertainments such as comedy talk or movie scenario. Perhaps it could be quintessence of all temporal art. In Classical music and jazz theory, it is more or less *believed* that prograding the cycle feels natural to humans, resulting in the “rules” of chord progressions (but of-course you don’t have to care of them).

Retrograding the Cycle

Admitting that prograding the cycle sounds natural, it doesn’t mean the reversed cycle T–D–S–T sounds unnatural. Each retrograding motion has unique character, which will greatly enrich chord progressions.

Especially the “cooling off” effect of D–S is not favored in Classics or jazz. But in genres such as rock, reggae or EDM it is commonly used. Prograding and retrograding are equally important in musical expression so don’t get any negative impression by the word “retrograde”.

6. Listen and Compare

Now listen to some 4-chord progressions and feel the differences of TDS. This time, I will use a single melody and apply many different chord progressions to it.

Normally, random reharmonization might not work musically. However, in this case, I meticulously designed a melody that works well with all the chord progressions shown here. I want you to experience how differently the same melody can sound when paired with various chord progressions!

T–S–D–T

Progressions starting with T and ending with T are the most stable scheme; you can offer the sense of rest in both ends. And prograding the function cycle is also an accustomed pattern, so it’ll sound very natural to most listeners.

These are some typical progressions constituting T–S–D–T cycle. Note again that III_m→I is not much used.

T–D–S–T

The retrograding cycle, T–D–S–T, draws a totally different tension-release curve. Right after T comes the peak, D. Then gradually release that tension.

I→V or VI_m→III_m creates a dramatic upsurge, while IV→I produces a mood of soft landing.

Turn Back

You can also go back and forth the orbit e.g. T–D–T–S, T–S–T–D.

The two progressions above are so famous that Wikipedia has an article on it.

S–D–T-*

Starting the cycle from S is also very common. Instead of offering the “rest” at the beginning, it starts with rather unstable state. So it’s fit for expressing any sort of mixed feelings such as broken-heart, anxiety, hesitation or even hope, tenderness etc.

2-5-1 is a fixture in jazz. Or in dance music you’ll encounter 4-5-6 quite frequently.

S–T–D-*

Retrograding the cycle from S results in S–T–D.

You can well reflect erratic emotions in these progressions—It starts with uneasy state, then gets relieved but soon intensively elevates.

D–T–S-*

Starting with D is uncommon, but occasionally used to bring dramatic elevation effect. Listeners don’t expect the peak to come at the beginning so it’ll be a good surprise.

You may not easily find actual examples of this pattern, so here’s a playlist of progressions starting with V or III_m.

Keep T Out

Not using T is another good strategy. Just iterating “heat up” and “cool down”, you can continue the floating state forever.

This endless feel is typically suitable for loop-style music such as Electronica, techno or hip-hop.

For example, “Super Shy” just repeats III_m–II_m. “Good Times” simply repeats II_m–V. The infinite loop of S and D without stabilization can be utilized to depict various scenes, such as vast landscapes, dreamy spaces, or all-night parties.

Cannot Introduce Everything

4-chord progression is a very standard format in popular music. Simply calculating, you can generate 6^4=1296 progressions just with the six prime chords! So exploring and mastering these patterns is extremely important. You don’t necessarily have to learn advanced chords to write a good song🙆