I love the smell of Sharpies markers in the morning.

Drew, sorry for the delay in getting back to you.

V of V could be used to modulate to a new key, but quite often it was used just as a single isolated chord within the overall chord progression.

As Beagle said, the key center could sometime change for a few measures.

Also, in longer classical compositions the key center could change quite frequently and vary widely during the middle development section of the piece, before returning to the original key near the end.

So.....

There are formulas for music composition?

Amazing.

The A7 is serving as a secondary dominant chord in the key of G. The movement of the progression is moving in 5ths. A7 is moving to D7. This is common. vii-iii-vi-ii-V-I. A dominant 7th chord can theoretically  be substituted for any diatonic minor chord moving a 5th into the next chord. Trust me. I live in a van down by the river. 

http://en.wikipedia.org/wiki/Secondary_dominant

Bapu uses his own, trademarked progression:  i, i, i™.

He doesn't have a circle of 5ths and 4ths, but more of a circle of Am's.

bayoubill


The A7 is serving as a secondary dominant chord in the key of G. The movement of the progression is moving in 5ths. A7 is moving to D7. This is common. vii-iii-vi-ii-V-I. A dominant 7th chord can theoretically  be substituted for any diatonic minor chord moving a 5th into the next chord. Trust me. I live in a van down by the river. 

http://en.wikipedia.org/wiki/Secondary_dominant

I like this answer.

I am always amazed at how much knowledge we have here at the forum.

Thanks to everyone who is keeping the discussion going.


One thing I would like to add, for people that might think theory only matters with "classical" music, is that many classical composers drew their inspiration from traditional and folk music that they heard played by street musicians.

I just want to point that out to remind us that classical music is not some extra special ivory tower genre... Classical music is deeply influenced by what humans tend to enjoy even without a knowledge of theory.


all the best,
mike

It's worth remembering that chord II with a major third, while technically still functioning as the secondary dominant, is very often used as a means of resolving to chord I directly via chord IIm, to the extent of being almost hackneyed.  E.g. Check out Girl From Ipanema, and the use of A7 in the Beatles' She Loves You.  It is quite common in Motown songs.  Using G as example key, the sequence A7-Am7-G (or, often, A7- Am7(5b) - G) , with each of those chords played over a G bass, is a very common move.

Many years ago, when I was in college, I tried to take a Music Theory class.  The professor told me that only pianists could learn Music Theory because they were the only "real" musicians.  He told me to drop the class.  I tried to stay in, but he told me that teaching me music theory would be like trying to teach a duck subatomic theory. 

I was depressed.  I went out and got a loaf of bread.  I went down to the river and sat on the bank.  I tore off a few pieces of bread and tossed them into the river.  A duck flew down, ate some bread and then climed up on the river bank next to me.  He stared at me for a minute, then walked over to a DeLorean parked nearby.  He climbed in, looked directly at me, held his wing up in an "L" shape over his forehead, and sped away.  To my surprise, his car vanished into thin air. 

I thought that was amazing, but then a frog hopped over to me and said, "Experimental Physicists always think they're hot stuff until they get themselves caught in a causality loop."  The frog croaked loudly, then yelled after the duck, "I'm not going to keep on bending time and space to get you back from the 1800's!  I've got a gig tonight!"  The frog pulled out a (very) short scale Gibson SG out from behind a tree, pulled his shades down, croaked once more, and then vanished with a bright flash.

I thought about it some, and then decided that perhaps music theory was over my head after all...