tonic-dominant vs tonic-subdominant

how to tell them apart

How do you know whether a progression is tonic-dominant or tonic-subdominant?

You’ll notice that in, say, C major, the tonic-dominant pair is C and G, and in G major the tonic-subdominant pair is G and C. They have the same exact chords, but somehow the relationship between them is different. Let’s explore how.

Looking at the individual notes in the chords, we have C E G in a C chord and G B D in a G chord. When we are in C major, those notes have the following “jobs”:¹

C  D  E  F  G  A  B
do re mi fa so la ti

In major tonality, the “job” of ti is to lead up to do, the resting tone/home note/tonal center/tonic. We often like to add the 7^th above the root of the dominant chord, to create a “dominant 7^th chord” — this would be the note F, which has the job fa — because fa’s job is to lead down to mi, which is the note that gives the major scale its major quality. So if one of the chords is a dominant 7^th and the other is not, then we are 99.9% of the time looking at a tonic-dominant pair.² And if you are playing along at home and you don’t know your dominant chords yet, play the regular version without the seventh and you’ll be fine. 

When G is the tonic of the major scale, the notes now have different jobs:³

G  A  B  C  D  E  F#
do re mi fa so la ti

Here C is now fa and therefore has the job of leading us down to mi, which is B. If we only use G and C, there is no ti in the harmony leading us back up to do. In a strict Western Classical Music sense, this is a weaker cadence because of the absence of the ti-do combination. Sadly, people have used this to then say that music that uses this cadence is somehow not-as-good, but we don’t say that here, because we know that’s ridiculous. 

The resting tone is emphasized a different way in songs that only use tonic and subdominant. The note that is common to both chords happens to be do, which makes it a drone of sorts that the other notes of the chords dance above. The common tone in a T-D progression is so, but with the ti-do action happening as the chords switch, we perceive do as the resting tone instead of the common tone of so. Melodies are also working to emphasize our perception of do as the resting tone, as well; we will explore that in an upcoming post.

That’s a nitty gritty explanation of what is going on with the chords. What are the other ways in which we make a home chord sound like a home?

• it has the most air time [e.g. “Ceniv u popa,” “Day-O,” “Clementine”]

• it happens in places of rhythmic importance, e.g., the end of the whole song; a cadence; the beginning of the song or phrase⁴

You can use both strategies, but you can also use just one of them and it will be enough to convince a listener of the primacy of one pitch set over another.

Yet, there’s another issue: What if the chords are paired evenly and symmetrically, as in a shuttle, counterpoise sandwich, or counterpoise inversion? Since the two chords get the same amount of air time, we have to look at places of rhythmic importance, and particularly what is going on in the melody. In a counterpoise sandwich and a counterpoise inversion, the tonic appears at both the beginning and the ending of the phrase, that is, the two places of rhythmic importance. In a shuttle, it can be more difficult. However, most shuttles begin with the tonic and at the end of the song, it either fades out or ends on the downbeat of the beginning of the shuttle, that is, the tonic.⁵ When all else fails, listen to what the melody is doing and where it seems to come to rest.

Tagg proposes two other possibilities: a) there is only one chord, or b) there are two chords but there is no tonic. In the first case, the resting tone is usually omnipresent as a drone or, in classical parlance, a pedal — I touched on this above. In the second case, the perception is in the ear of the “behearer.” I tend to hear no tonic/two poles more if each chord is in play for longer than what would be considered a shuttle (see Life During Wartime) or if there is no real linear melody — we haven’t looked at any songs/pieces like that, but we might find them in more dance-oriented techno-related styles, perhaps some rap songs, or in the more experimental corners of minimalist classical music. But! You may hear things more like Tagg does and that is fine.

1. La is not involved in the C or G major chords, but it just makes more sense to look at the whole scale or pitch set.

2. There are always exceptions, especially when you can’t think of any.

3. Also, you’ll note that we now have F# and not F natural.

4. That said, it's a common compositional device to play with this expectation and foreshadow or delay putting the tonic in the place of rhythmic importance. We hear that less in two-chord songs and more often in pieces with more harmonic action.

5. The third option is what Tagg calls the counterpoise kickback, in which the shuttle doubles its frequency for a measure enabling the phrase to end on the tonic. We’ve seen so far only examples in which it looks like there’s going to be a shuttle, but the next phrase immediately goes into the kickback. I understood the original idea to be that the shuttle lasts long enough to be recognized as such, whereas in, say, Skip to My Lou, or the alternate progression in Day-O, there’s one volley back and forth before it goes into the quick switcheroo; Drunken Sailor opts for a quick sandwich, instead.