Secondary dominant question

rsvmark

I have a question.

Harmonising in thirds, the V chord is a dominant 7. So for example, if the I chord is a C, the V chord is a G. The secondary dominant is a fifth of the fifth, so a 9th or actually second of the original tonic, in this case a D.

is the secondary dominant called that because it’s the second dominant (the first being the V or G chord) or is it because it’s tonic is the 9th, or actually the second note of the C major scale.

viz

It’s because it’s not the primary dominant chord (which refers exclusively to the V chord), but a secondary one. Nothing to do with the 2nd or 9th.

A secondary dominant is any chord (at least in a major key) that’s not the V chord, but is adjusted to perform like one, with a major 3rd and a minor 7th, therefore enabling a strong resolution up a 4th to another chord in a “perfect cadence”, in the same way that the (primary) dominant chord can resolve up a 4th to the tonic.

Your example of D7 is indeed the dominant of the V, and that’s the one most people think of when they think of secondary dominants. It’s the one that changes a ii-V-I to a II-V-I (or II7-V-I)

But other secondary dominants exist. Taking the key of C:

A7: the dominant of Dm (VI7 - ii)
- as in I Got Rhythm (C-A7-Dm-G)

B7: the dominant of Em (VII7 - iii)
- as in Just the Two of Us (C-B7-Em)

C7: the dominant of F (I7 - IV)
- as in a blues (C-C7-F)

E7: the dominant of Am (III7 - vi)
- as in That’s Life (C-E7-Am)

rsvmark

Thanks @viz ;

So if it’s not related to the II or the 9th per se, and it’s used to create tension and resolution to another chord, can you use it anywhere?

viz

Yes you can resolve to any chord by preceeding it with ITS dominant, whereby you get a secondary dominant “functioning” as a dominant. 

Classic example is a “backcycling” 36251, which would be E7-A7-D7-G7-C. All are secondary, apart from the G7 which is primary. It’s called backcycling because it’s going anticlockwise round the circle of 5ths. Or to put it another way, doing a circle of 4ths. 

Btw, the longest backcycle I’ve heard is ACDC’s Can I sit next to you girl at 2:41 here:

https://youtu.be/5FJLGGVevAw?si=nUaBQI51B-LPYwDV

It’s downtuned but: D - G - C - F - Bb - Eb - Ab - Db - Gb

rsvmark

Bingo, thanks @viz ;

digitalkettle

viz said:

Yes you can resolve to any chord by preceeding it with ITS dominant. That’s a secondary dominant “functioning” as a dominant. 

Classic example is a “backcycling” 36251, which would be E7-A7-D7-G7-C. All are secondary, apart from the G7 which is primary. It’s called backcycling because it’s going anticlockwise round the circle of 5ths. Or to put it another way, doing a circle of 4ths. 

Btw, the longest backcycle I’ve heard is ACDC’s Can I sit next to you girl at 2:41 here:

https://youtu.be/5FJLGGVevAw?si=nUaBQI51B-LPYwDV

It’s downtuned but: D - G - C - F - Bb - Eb - Ab - Db - Gb

Great example...I'm being Mr Pernickety but that 'Can I Sit Next To You' sequence is:
G C F Bb Eb Ab Db Gb -> resolve back to G -> then to A for the chorus refrain thingy

viz

digitalkettle said:

viz said:

Yes you can resolve to any chord by preceeding it with ITS dominant. That’s a secondary dominant “functioning” as a dominant. 

Classic example is a “backcycling” 36251, which would be E7-A7-D7-G7-C. All are secondary, apart from the G7 which is primary. It’s called backcycling because it’s going anticlockwise round the circle of 5ths. Or to put it another way, doing a circle of 4ths. 

Btw, the longest backcycle I’ve heard is ACDC’s Can I sit next to you girl at 2:41 here:

https://youtu.be/5FJLGGVevAw?si=nUaBQI51B-LPYwDV

It’s downtuned but: D - G - C - F - Bb - Eb - Ab - Db - Gb

Great example...I'm being Mr Pernickety but that 'Can I Sit Next To You' sequence is:
G C F Bb Eb Ab Db Gb -> resolve back to G -> then to A for the chorus refrain thingy

Yep but I included the last note of the previous bar, which is also a 4th below the start, and I stopped at the final 4th 

mine: D - G - C - F - Bb - Eb - Ab - Db - Gb
yours:       G - C - F - Bb - Eb - Ab - Db - Gb - G - A

digitalkettle

viz said:

digitalkettle said:

viz said:

Yes you can resolve to any chord by preceeding it with ITS dominant. That’s a secondary dominant “functioning” as a dominant. 

Classic example is a “backcycling” 36251, which would be E7-A7-D7-G7-C. All are secondary, apart from the G7 which is primary. It’s called backcycling because it’s going anticlockwise round the circle of 5ths. Or to put it another way, doing a circle of 4ths. 

Btw, the longest backcycle I’ve heard is ACDC’s Can I sit next to you girl at 2:41 here:

https://youtu.be/5FJLGGVevAw?si=nUaBQI51B-LPYwDV

It’s downtuned but: D - G - C - F - Bb - Eb - Ab - Db - Gb

Great example...I'm being Mr Pernickety but that 'Can I Sit Next To You' sequence is:
G C F Bb Eb Ab Db Gb -> resolve back to G -> then to A for the chorus refrain thingy

Yep but I included the last note of the previous bar, which is also a 4th below the start, and I stopped at the final 4th 

mine: D - G - C - F - Bb - Eb - Ab - Db - Gb
yours:       G - C - F - Bb - Eb - Ab - Db - Gb - G - A

A-ha...consider it unpernicketied!

We play that tune almost every gig and I've had to embed that section in muscle memory

HAL9000

rsvmark said:

Thanks @viz ;;

So if it’s not related to the II or the 9th per se, and it’s used to create tension and resolution to another chord, can you use it anywhere?

Turns up In blues occasionally as….

I    I   I   I
IV IV I   I
II   V I   I


…off the top of my head this is used in John Mayall’s ‘So Glad’ (from the Road Dogs album).

viz

HAL9000 said:

rsvmark said:

Thanks @viz ;;;

So if it’s not related to the II or the 9th per se, and it’s used to create tension and resolution to another chord, can you use it anywhere?

Turns up In blues occasionally as….

I    I   I   I
IV IV I   I
II   V I   I


…off the top of my head this is used in John Mayall’s ‘So Glad’ (from the Road Dogs album).

Nice. And the dominant of the ii turns up in jazz blues in the 6251 turnarounds. 

I     IV      I       I
IV   IV     I       VI7
ii     V    I-VI7  ii-V

(The 2 chord can be a II7 as well but it’s normally a standard ii.)

And a Count Basie blues will typically go one further with a 36251:

I     IV       I         I
IV   IV      III7     VI7
ii     V    III7-VI7  ii-V

viz

Just wanted to add something about secondary dominants in minor keys. 

So far we’ve been talking about C MAJOR. 

In a minor key, it’s the same, the V chord is still the “primary” dominant, which in the case of C minor would be G7. 

Now, as we know, in minor keys, the 5 chord naturally a minor chord, a “v” not a V. Harmonising the C minor scale gives us G minor as the 5 chord. It needs to be altered, majorised, to turn it into a proper G7. Its Bb is converted to a B. But that doesn’t mean it’s a secondary dominant.

In the same way, the VII chord in C minor is a Bb7 chord. It looks like a dominant 7th chord, but it’s not, it’s just the diatonically correct 7 chord of a minor key. If however it is being used to resolve up a 4th to the relative major, like in a modulation to establish Eb as the new tonic, then you could call it a secondary dominant, even though no notes had to be altered to make it perform like one. 

I purposefully did all the above in C minor, but it might be easier to understand in A minor:

So the 5 chord in A minor is naturally E minor, but can be converted from v to V by sharpening the G note to G#. That new E7 chord is still “the dominant 7” of A minor. 

Conversely, the VII7 chord, the G7, already looks like a dominant chord, but it’s not, it’s the sub-tonic. If it’s being used in a VII7-III modulation, you could call it a secondary dominant, even though it’s not had to be changed in any way.

Dunno if that’s interesting or of use to anyone!

Stuckfast

So, taking this to its logical conclusion, this sort of chord sequence is quite common:

I       I7      IV      I

Is the I7 a secondary dominant here?

viz

Yep, as per my first post, that’s definitely one of them. 

In our world of rock and blues guitar, mixolydian is very common, where the I chord has a flat 7 already, facilitating that I-IV progression. And the 5 chord, which is supposed to be minor in mixolydian, is usually majorised anyway, so you get a primary dominant too. 

rsvmark

@viz Just when I think I have it sorted, you pull me back in!

rsvmark

Just spent some time harmonising in 3rds on the C major and minor scales.

Recap. I get that harmonising in C major gives the V chords a dominant chord (G B D F) or tonic 3 5 b7. 

If i harmonise the natural Cmin scale (C D Eb F G Ab Bb), the i iv and v chords are all minor 7 chords thusly:

i is C Eb G Bb
iv is F Ab C Eb
v is G Bb D F

So i can see why changing the Bb to a B makes it a G7. Strictly speaking, it’s leaving the key because as you say, the Bb has gone to a B temporarily.

Am i right in thinking that C MELODIC minor is:

C D Eb F G Ab B so you are temporarily shifting key to that or C major over the G7 until you resolve to the Cmin as the i chord? It still has a great cadence.

i now need to lie down in a dark room before we start on secondary dominants in a minor key!

joeW

C melodic minor has a major 6th ie A Nat.  

rsvmark

Ooops, sorry. I meant harmonic minor which is natural minor with a raised 7th. 

viz

rsvmark said:

Am i right in thinking that C MELODIC minor is:

C D Eb F G Ab B so you are temporarily shifting key to that or C major over the G7 until you resolve to the Cmin as the i chord?

Not quite. What you wrote is C harmonic minor, with the special note in bold. 

C D Eb F G Ab B C

C harmonic minor means you raise the 7th. But that’s really a bit misleading. Harmonic minor is a device that shows you the notes in the harmony (ie in the chord) of the dominant. That’s what it’s for. So when the 5 chord is playing, it’s telling you that you can raise the 3. So the G7 chord can be majorised. Like you said above. That’s what harmonic minor is all about. And because it’s only talking about the harmony - ie the chord - it has nothing to say about the 2. It’s only interested in the 1,3,5,7, i.e. the G, B, D, F. It’s not interested in the Ab. So in the harmonic scale, the Ab stays flat. And it’s spelt out and practised from C to C, but it concerns what happens when you’re thinking about the V chord. 

Melodic minor is when, on the dominant chord, you also raise that 2 note, so you get a melody over the dominant that not only has the majorised 3rd, but also doesn’t have a flat 2, so you avoid that awkward augmented 2nd interval between the 2 and 3 that you would otherwise get in harmonic minor, which would have left the 2 as it originally was, an Ab. So, just like you would have in C major, over the dominant you get G, A, B, C, D, Eb, F, G.   Ok the Eb is still flat, because you’re still in C minor, but the tune now has a raised 2 and a raised 3. So it works over the majorised dominant chord, as a tune - a melody. 

Now when people say “C melodic minor”, they spell it from C to C, so they write C, D, Eb, F, G, A, B, C. But that again is a bit misleading because the whole purpose of it is to tell you want you can do over the Dominant, G. And the tradition is that you play it ascending as though the dominant chord were being played; and then at the top of the scale you assume a perfect cadence from G7 to C minor occurs, so that on the way down, everything’s collapsed again to natural minor, so the 6 and 7 are flattened again. The special bit about melodic minor has nothing to do with what’s played on the tonic, C. 

Edit - ah, I see that in the time it took for me to write a vastly overblown and unnecessary reply, you’d sorted it

joeW

rsvmark said:

Ooops, sorry. I meant harmonic minor which is natural minor with a raised 7th. 

Ah yes indeed. 

rsvmark

So my journey into secondary dominants continues. Let’s stay in a major key for today.

we know the primary dominant on the 5th degree of the scale resolves to the I chord. So can you use the following secondary dominant chords to resolve to different degrees of the scale:

Staying in C major:

A7 to resolve to Dmin (ii chord of C)
B7 to Emin (iii chord and very oasis)
C7 to F (IV)
D7 to G (V)
E7 to Amin (vi)

So what’s the deal when you come to a diminished chord? Would you ever encounter a circumstance when you might use a secondary dominant to resolve to the diminished chord?

Tia and apologies if this appears a meander…. It’s the way my head works

Edit: Q2 - do dominants always have to resolve to the 4th above?

Example:
Honky tonk women is G C G A7 D. The A is the 2 chord (so should be an Amin) but acts as a secondary dominant (A7) to go to the D which resolves in a perfect cadence to G.

(Relevant for @viz as we have history here.) Creep by Radiohead is G B C. The B is the third chord in the scale of G major and should be Bmin. It’s not so B is acting as a secondary dominant? That then should resolve up a 4th to E which as the 6 chord in G major should be Emin. But it doesn’t. The B resolves to a C. So is the B a secondary dominant even though it resolves up a half step or is it something else (change Bmin to B )?

rsvmark

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