So, why are the I, IV and
V chords so important?
For this explanation, I'm hoping that you
have a basic understanding of intervals and chords, if not,
hold off until you've learned about intervals in the interval
Basically, all harmony in western culture
is an artificial construct, based on hundreds of years of
people figuring out what sounds good and turning that into
habits. Back in the old days, and we're talking about the
very old days, people were just coming out of the dark ages.
Anything that even resembled knowledge seemed like something
mystical and wonderful. Anyway, some of the earliest knowledge
that started making its way back into the World came from
Greece. Among the many philosophers and thinkers from Greece,
one that had particular sway over many was Pythagoras.
Pythagoras was a mathematician responsible
for discovering many things that are very common place in
today's math. However, he also held that numbers were mystic
to large degree. So, this whole school of mysticism sprung
up around Pythagoras. Some of his mathematical theories
applied to music and the mathematics of vibrating strings.
For Pythagoras, the relationship 3/2 created the interval
which we know as the fifth. For Pythagoras, this relationship
had certain mystic qualities.
Anyway, let's move forward to around the
year 1200 or so. The main places where knowledge was being
sought and stored was monasteries. Monasteries are usually
occupied by monks (a little joke). Some of these monks got
a hold of the teachings of Pythagoras and thought that they
were very cool, and this whole idea that music and mathematics
could be joined and become something mystic. They were also
in particular awe of this relationship 3/2, cause to them,
the number 3 signified the trinity and other things spiritual.
Remember, these are monks, and there was no pop music, if
you had music, it was going to be sacred music. So, since
this relationship of 3/2 yielded the interval of the fifth,
they decided to build a whole tuning system around fifths.
This system of intonation built on fifths
became known as Pythagorean tuning. In a system where fifths
rule, fifths are the main consonance and also, fifths are
the main interval. Movement from one chord to another is
also in fifths, and those chords that are a fifth away from
the main key center are going to be considered the strongest.
If you click here you can see that if you're in the key
of C, a fifth going up gives the note G and a fifth going
down gives the note F. So most of the chords in your composition,
if you're in the key of C are going to be the C, F and G
chords. The 2 strongest chords are the C and the G.
Pythagorean tuning and tunings based on
this system were around for hundreds of years and during
that time the habit of moving chords in fifths was firmly
established. There was another good reason for chord movement
in fifths. Chords moving in fifths yielded the greatest
number of common notes and nearest notes, so harmonic movement
was very smooth.
There was only one drawback to Pythagorean-based
intonation. It didn't work for all keys. If the intonation
was built around the C note, the keys of Ab and Gb sounded
awful. They were very out of tune. So, if you were a composer
in those days you avoided those 2 keys. Another thing is
thirds didn't sound that good either in Pythagorean intonation,
so a lot of the masses written during that time, the last
chord is usually just open fifths, with no third.
Anyway, at some point, people I'm sure got
fed up with the fact that you couldn't write in all keys
with Pythagorean intonation. In the 1500s, a method of intonation
called meantone tuning came into being, which was more flexible
than Pythagorean tuning, but not as pure. The Renaissance
was kicking in around this time too and people were experimenting
with all sorts of things, including new music. By the 1600s,
meantone tuning gave way to a a new tuning called equal
Equal temperament basically made all the
notes a little out of tune. But thirds now sounded better
and all keys could pretty much be played, even though they
were all a little out tune. Some composers at that time
embraced this new equal temperament, particularly one by
the name of Johann Sebastian Bach. He went ahead and wrote
a couple of works for keyboard in all keys. Among these
were the Well Tempered Clavier Books I and II and the 2
and 3 part inventions.
And in all of these works, as in the works
of those that came after Bach, like Haydn, Beethoven, Mozart,
to name a few, this relationship between the I and the V
chord was still supreme,this was the one chord progression
to top all chord progressions, as well as various progressions
of chords in fifths.
And so, when you look at the music of western
culture, those 3 chords still rule folk music, blues, rock
and roll. It's a tradition and a culture that has been handed
down to us through hundreds of years of use. And it still
works fine today, if one is to look at the number of songs
written just using 3 chords.