How to know which chords to play

Let’s say that after learning the basic chords on the guitar, your other guitar-playing friend invites you to a jam session. You show up with your cheap starter acoustic guitar and sit down to play, head held high with confidence that you can play any chord your friend needs. That’s when your friend says, “alright, let’s jam in C. You play chords first”, then proceeds to count off, expecting you to start strumming whatever comes to your head. If all you’ve ever done was learn separate chords, you will most likely jump to the C chord that you practiced, then proceed to draw a blank as to what to play next. If you read this post and put some effort into learning the content, I assure you that will never happen again.

In order to strip this down to the fundamentals, let’s take a look at the C major scale written out on a staff.

Now, if you’ve read my post on chord theory (or just know the basics of chord theory already), you know that basic chords contain a root, a 3rd, and a 5th. Let’s add those to each of the notes above, but let’s make sure we use only notes from the C major scale (which we know, from basic scale theory, contains no accidentals).

The chords that each group of three notes produce are written on top of the staff in the image above. C, E, and G make a C major chord, while E, G, and B make an E minor chord (it is minor because of the G. If it were a G#, it would be an E major chord. At some point I’ll make a post that talks more about what notes are in each key). For those of you who have trouble reading music notation, here is a list of what is shown above:

Measure 1: Contains C, E, and G, making a C major chord

Measure 2: Contains D, F, and A, making a D minor chord (D major would be D, F#, A)

Measure 3: Contains E, G, and B, making an E minor chord (E major would be E, G#, B)

Measure 4: Contains F, A, and C, making an F major chord

Measure 5: Contains G, B, and D, making a G major chord

Measure 6: Contains A, C, and E, making an A minor chord (A major would be A, C#, E)

Measure 7: Contains B, D, and F, making a B diminished chord (B major would be B, D#, F#)

The roman numerals at the bottom of staff are used to indicate which scale degree the chord is attributed to, as well as the quality of the chord. Upper-case numerals represent the major quality while lower-case represents minor. For example, the numeral “IV” can be interpreted as “the major chord built off of the fourth scale degree”, and the numeral “vi” can be interpreted as “the minor chord built off of the sixth scale degree”. The quality of chords built off of a standard major key will always follow this pattern. Learn it, memorize it, love it, live it:

Major, minor, minor, major, major, minor, diminished

To further prove this, let’s look at the key of Bb major, which contains the two accidentals; Bb and Eb (I’ll explain how I know that in a future tutorial. For now, if you don’t know what accidentals are in each key, refer to my post on basic scale theory to get yourself started). First, like the example above, we will begin with the scale written out on a staff:

Now let’s stack those thirds on top of each note. Remember, since we are in Bb major, any B or E encountered must be flattened!

Amazingly, the chords that are produced follow the exact same pattern I showed you above. The three chord (iii) is minor, the five chord (V) is major, the one chord (I) is major, etc.

So what does all of this mean?

Let’s say you’re jamming with your friend. He is improvising in the key of Bb major. As long as you have the order of chord qualities memorized for a major key, you can whip out any of those chords during the jam session. Start at a Bb, then move to a Gm, then an Eb major, then an F major (I just outlined a very common chord progression known as I-vi-IV-V, or 1 6 4 5). It makes sense when you think about it. We build these chords using only notes from that particular key, so scales being played in that key should sound good* on top of them. Or let’s say you want to write a song. Remembering this order of chord qualities will greatly help you with coming up with a chord progression for the song.

*Disclaimer: “Good” in the sense that they technically work. What sounds good musically to someone is rather subjective, but most people will agree that a major scale played over the chords extracted from the scale sound “correct”.

I realize that this is an oversimplification of this topic, but I think it is a good place to start if you are new at improvising chords. I will certainly make expansions to this tutorial in the future (talking about the different modes, chord movement, specific scales that sound more “in” on top of each chord, adding sevenths to each chord, etc) and I may also re-vamp and improve this post, so stick around.

All feedback, positive and constructively negative, is welcome!


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