Why is it so important for you to know your keys in music?
Using the process of elimination.
Yes, there was a time when the internet didn't exist. I remember that time very well. In fact - for the first 36 years of my life, I managed to live my life without the internet. That means that in order for me, as an instrumentalist, to learn how to play songs on the guitar, I had to know a certain amount of music theory in order to understand basic structures in songs. I had to know my chords - as many as I could remember. I had to know where those chords belonged in their keys. I didn't have the convenience of the internet or YouTube videos to help guide me. I had to figure it out by listening and learning my keys.
Why is this important?
When I started taking guitar lessons, my teacher mostly had me read notation out of an "Alfred Guitar" book. Honestly, I hated that book. It was boring. I was much more interested in learning songs and improvisation. My teacher and I compromised. We did half the lesson in theory from the book and the other half in learning chords and songs. Somewhere along the line, I realized that I could pick out chords just by listening to the song. You see, back in the late 1970's, the only way that I could learn how to play songs was to record them from the radio onto a cassette tape. This way, I could figure out every chord as I played the tape, over and over again. One day, it occurred to me that there were patterns in these chord progressions. Certain chords were grouped together - sort of like a family. My teacher did his best to explain that these groups were called "keys".
Common chords in keys.
I eventually figured out that every major and minor chord in the twelve keys in music, exist in three different places. For example, the A minor (Am) chord is the second (ii) in the key of G major, it is the third (iii) chord in the key of F major, and the sixth (vi) chord in the key of C major. I remember writing out all of the chords by hand, and figuring out the structure of all of the keys and chords that I knew.
Here is a diagram of all of the keys normally used in all music, including the odd keys like Cb, Gb and C#. The keys you should learn as a guitar player are as follows:
C, G, D, A, E, B, F#, Db, A, Eb, Bb and F.
Each Roman numerical interval has it’s own “type” of chord:
I, IV and V are all major chords. II, III and VI are all minor chords, and the VII chord is diminished. Every key in music has three major chords, three minor chords and one diminished chord.
Ear training.
Necessity being the mother of invention, I had to learn the hard way. If I wanted to figure out songs, the only way I knew how to do this was to train my ears to listen for repeated chord progressions, recognizable song structures and common music formulas. I eventually learned how to listen for and anticipate a chord in a song by using the process of elimination. If I heard a new song on the radio, I'd try to pick out the chords, just by listening to the song.
For example...maybe the song had a G and a C in it. Okay, so which key is that? Well, we don't know yet, because we don't have all of the information. The chorus would begin and there would be a couple of minor chords in the song. One was Am and the other was Em. We still don't know which key the song is in, but we have it narrowed down to two: "G and C".
We’re missing just one more chord to tell us which key this song is in. If the missing major chord is D, the song is in the key of G. If the missing chord is F, the song is in the key of C.
We missed that D chord in the first verse. So, now we know that this song is in the key of G. This was how I initially figured out songs. I knew which chords belonged in which keys, so that helped take away a lot of the mystery.
I had to listen for every chord to determine which key the song was in. I also had to train my ears to listen for the "type" of chords that were being used in the songs. Was that a minor or a minor seven chord? Was that a major seven or a major nine chord? Where was the chord being played on the fretboard? Is the voicing in that chord the same as in the song? All these nuances had to be learned. Now, imagine doing this process several hundred times over many years as a way to learn how to play and memorize thousands of songs. This was when I learned how important it was for me to know and understand all twelve keys in music. It was simply the process of elimination. Not only could I figure out the chords in a song, I also knew which chords to anticipate as I was learning that song. I learned how to write out chord charts in song structures that other musicians could read. It wasn't a perfect system, but it worked for what I was doing.
The number system.
I learned the importance of numerical placements of chords in keys, several years later. Honestly, I really didn't know there was such a thing. Lead sheets and chord charts were what the pros used for gigs and rehearsals. Instead of writing out chords, they wrote Roman numerals. (i.e. IV, xi7, ii7, V7, I, etc…)
I didn't know that this was a thing. I knew how to listen for chords and figure out the keys, but using Roman numerical intervals never occurred to me. When I started teaching lessons in 1996, I had to literally start over from scratch. I had to relearn music theory. Since I was teaching at Sam Ash music store, I was fortunate enough to have access to every possible music theory book for guitar, in the store. Again, this was three years before I was ever on the internet. I read those books cover to cover, over and over until I could teach it. That's the thing about teaching - there is no better way to learn anything than to teach it. For me, it was fairly easy to read and study; and I learned just how important the circle of fifths/fourths in music truly is.
The Circle of Fifths.
The most popular chord progressions in music.
When you understand the Roman numerical intervals (or placements) in every key, this also solves much of the mystery of almost any song structure. Arguably, one of the most common chord progressions in music is the "I - vi - IV - V". These four intervals can literally be played in any order, and sound good. This four chord structure has been around since the 1950's. It is pleasing to the ears - and it also seems to be the perfect formula for millions of songs.
The "I - vi - IV - V" applied to any key, gives the song all three major chords in the key, and one minor chord for balance or tension. This formula also comes from an even older pattern used in "Blues" music. Blues primarily uses the I - IV - V in any key, as a standard or universal understanding amongst all musicians. Blues music has almost always been played in 8, 12, 16 bar frames that get repeated. Adding one minor chord to this structure is where I believe popular music originated. Rock and roll, country and other popular music needed more than this repeating structure. So, they added the fourth chord as the minor. This way, the songwriter had room to build a song around a verse, chorus, bridge structure.
(I won't go into detail about traditional jazz music for this article as it is a much deeper well that I will need to save for another article).
As songs progressed over the years, they became more and more sophisticated in their structures. The Beatles introduced seemingly endless possibilities in song structures that hadn't been seen or heard before in popular music. It has been long since understood that if you want to learn how to play music on the guitar or piano, just get yourself a Beatles song book.
The "singer/songwriter" era of the 1970's introduced many songs with jazz chords in their structures. This was the expansion period for breaking out of the common "I - vi - IV - V" structure and adding many more chords, including jazz chords. Some of those chords were borrowed from other keys. One of the more common practices then was changing the key during the song. Barry Manilow was notorious for this.
Every key in music gets played in music. There are however, some more popular keys for certain instruments. Guitar players like to play the chords in the keys of C, G and D. Horn players like to play in the keys of Bb, Eb and F. It doesn't really matter which key you like to play in. You should at the very least learn how to play the basic triads and seventh chords for as many keys as possible. Many keys on guitar require using "Barre" chords.
You can learn more about these types of chords here.
Study, apply, practice, write, learn and memorize as many chords as you can, and know their keys.
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