Unexpected chord in a song

Cranky

viz said:

Cranky said:

viz said:

No flat 7 chord in there. One thing he might be doing (though it’s hard to tell here with the washing machine going and the dog barking) is when he goes from the I chord to the IV chord (E to A), he may suddenly slip in a transitionary E7, in order to smoothen the transition from E to A. This is called a secondary dominant. Because it behaves like a V-I, whereas in fact it’s a Ib7 - IV. 

That E7 would have a D in it, rather than the D# which is played throughout the majority of the song. 

But there’s no actual D chord anywhere. 

So is there a difference between calling this a "secondary dominant" vs calling it a "modal mixture", as in a temporary lapse into E mixolydian?

Yes, because the flat 7 of E mixolydian does not facilitate the perfect cadence to the IV; the E as a root (I) chord is firm and absolute. Whereas in a Ib7-IV progression, the IV is treated in that instant as a I, and the progression behaves like a temporary V7-I cadence. 

Okay, so in E Mixolydian it would be a V-I progression whereas in E Ionian it would be a "temporary V7-I" progression?

Is this a substantial difference, or is it more nominal?

viz

Cranky said:

viz said:

Cranky said:

viz said:

No flat 7 chord in there. One thing he might be doing (though it’s hard to tell here with the washing machine going and the dog barking) is when he goes from the I chord to the IV chord (E to A), he may suddenly slip in a transitionary E7, in order to smoothen the transition from E to A. This is called a secondary dominant. Because it behaves like a V-I, whereas in fact it’s a Ib7 - IV. 

That E7 would have a D in it, rather than the D# which is played throughout the majority of the song. 

But there’s no actual D chord anywhere. 

So is there a difference between calling this a "secondary dominant" vs calling it a "modal mixture", as in a temporary lapse into E mixolydian?

Yes, because the flat 7 of E mixolydian does not facilitate the perfect cadence to the IV; the E as a root (I) chord is firm and absolute. Whereas in a Ib7-IV progression, the IV is treated in that instant as a I, and the progression behaves like a temporary V7-I cadence. 

Okay, so in E Mixolydian it would be a V-I progression whereas in E Ionian it would be a "temporary V7-I" progression?

Is this a substantial difference, or is it more nominal?

No, in E mixolydian, the E already has a flat 7, so E to A (or E7 to A) is just I-IV - ok it has a flat 7, but there’s nothing special about that fact coz it’s in the key anyway. 

What’s notable about the E major situation however, is that there is a D# in the key, so if you were to play the 7th note while playing the E chord, you’d be playing Emaj7; BUT when you prepare to move to the A, you can, especially in blues and folk, introduce a flattened 7th, so the I-IV sounds a bit like a V-I, in other words, just for an instant, the A sounds like the new home key, and the E7 sounds like its Dominant. This is why it’s called a secondary dominant, which is a fancy term for what is a very simple and natural move - just playing E7 before the A. 

Axe_meister

The C is the first, the F the 4th the G the 5th. The Bb is the flat 7.
You are immediatly in the territory of harmonizing the Mixolydian scale.
It so happens that in western Music the C major scale is thought of as the most important scale, so we tend to 
think of that as the main scale.
Probably because C major is easy to spell and it is just the white notes on the piano. For some reason we decided to start on the C. If we start on the A we are immediatly in Aolian mode or the natural minor.
Start on the G (again same white notes) and we are in Mixolydian.

So yes the song is in C. But C mixolydian rather than C major.
I'm really starting to think of modes as keys, rather than modes of a particular major scale.

HAL9000

Apart from the 'borrowed' chord explanation, there's also the fact that a lot of blues/blues-rock uses chords based on the minor pentatonic scale. For instance the C minor pentatonic consists of C Eb F G Bb, so a blues/rock that centres on C might well contain Eb and Bb chords (as well as the expected F and G chords).

Barney

It could be borrowed from key of F ..but sometimes you don't have to have a reason for things to sound right ...it's just they do ...iff it sounds good to your ear it's good ..theory shouldn't really need to come into it 

Roland

Theory is just a way of trying to explain what’s going on.