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If you've been playing the ukulele for awhile and maybe have tried your hand at songwriting, you may be wondering why it is that certain groupings of chords always seem to be together. Or maybe you've heard other players say things like, "play the I, IV and V chords in the key of G", and wondered what on earth they are talking about.
The key of C is always "home base." It's typically the first chord you learn, the first major scale, and you may have heard of the term "middle C" on the piano as a reference point. There is a reason for this. If we were to assign all of the natural notes in the chromatic scale in order C would be 1, D would be 2, E would be 3, F would be 4, G would be 5, A would be 6, and B would be 7. This is where the fancy Roman numerals come from. In the Key of C, the I chord would be the C chord, the IV chord would be the F chord, and the V chord would be a G chord. The I, IV, and V chords in any key are typically the most used chords in Western music, with a relative minor chord (Am) thrown in. This is why you will often see beginner ukulele tabs with the chords, C, F, G and Am in them. They are some of the easiest chords to play and the I, IV, V chord progression or grouping in any key is the most common.
How do they come up with the relative minor chord? A relative minor is always a sixth higher than the root. So in the scale of C, C is the root note and the A note is six notes higher, so Am is the relative minor of C. In the scale of F, D is a sixth higher, so Dm is the relative minor of F.
What about those other Roman numerals? Well, as mentioned before, each note has its assigned number, so a ii chord in the key of C would be a Dm. A iii chord would be an Em, a vi chord would be and Am, and a vii chord would be a B diminished. The Roman numerals are always lower case to denote that they are minor chords and the major chords are always capitalized in every key. The only exception to this is the vii chord which is always a diminished chord. So in the key of C, it would be B diminished.
What if you want to the I, IV, and V chords in a key other than C? Well, this is why it's handy to know your major scales. The D major scale contains the notes D, E, F#, G, A, B, and C#. So if we assigned the notes a number between 1 and 7 would be D=1, E=2, F#=3, G=4, A=5, B=6, and C#=7. So that means the I chord in the key of D is a D chord, the IV chord is a G, and the V is an A, and the Bm chord is the relative minor because it is the 6th note in the scale, or a sixth higher than D.
Does this leave you shaking your head? Luckily, there is something called the Circle of Fifths, which is a handy diagram that can simplify this information for you without requiring you to memorize all of the notes in each major scale (although that's not a bad goal for down the road). Check out this handy diagram.
Here's how you read this diagram. Every major key is listed in the pale pink outer wheel. Select any key to find the I, IV, and V chords. The ii, iii, and vi relative minor chords are listed in the light blue inner wheel. If you select C, the IV chord is found on its left (F) and the V chord is found on its right (G), and the relative minor chord is directly beneath C in the blue inner wheel. (Am). Dm is the ii chord and Em is the iii chord, also on the blue inner wheel. This pattern repeats all the way around the wheel. For example, in the key of G, G is the I chord, C (to its left) is the IV chord, and D (to its right) is the V chord. The relative minor is found directly beneath the G (Em), and the ii chord is Am and the iii chord is Bm.
If this still doesn't clear things up for you, there is also a linear chart with the chord families listed as well that might be easier to memorize below. All of the I, IV, and V chords are highlighted in blue and the relative minor chord is always the vi chord.
Now, here's a little trick for you that will help you start memorizing the I, IV, and V chords and relative minor in any key. Take this song, Runaround Sue, https://scorpexuke.com/pdffiles/Runaround_Sue.pdf which has the chords C, F, G, and Am in it. Then see if you can transpose it into the other major keys. Depending on your skill level as a player, this might introduce you to some chords that are tricky to play, so feel free to choose just a few keys with chords you can easily fret to start. Use the Circle of Fifths or this chart above to help you out!
Want to know more about how chords are made up? Please check out this other post for more details on understanding Major Triads and Minor Triads.