Of course, as with almost all musical concepts there are very few instances of always. What I mean by that is you can make educated guesses about which chords will be present but if there were hard and fast rules music would be very boring, indeed! A much better word is…. Usually.
Some time ago I wrote about how major diatonic scales are constructed and how the triads (chords) come out of those scales. Without getting into the concept of modes, it breaks down like this:
In any Major key, the I, IV and V chords are Major. The II, III and VI chords are minor. The VII chord is diminished, but in many instances in various forms of popular music the root of that VII chord is lowered by ½ step, turning it into a Major chord. This is usually referred to as the “flat VII chord.” Here are the scale-line triads (including a flat VII rather than the naturally occurring diminished chord):
Key of G Major (Major diatonic scale: G, A, B, C, D, E, F#):
G Major, A minor, B minor, C Major, D Major, E minor, F Major.
Another example. Key of D Major (Major diatonic scale: D, E, F#, G, A, B, C#):
D Major, E minor, F# minor, G Major, A Major, B minor, C Major.
Think about songs you may know in those two very common keys and I’ll bet the majority of the chords – if not ALL the chords – are listed. This is no accident. In Western music, for the last four hundred years or so melodic structure has been based for the most part on the Major Diatonic Scale and the chords above are constructed on ONLY notes in a given key (the exception being that bVII chord, which includes one note – the root – not in the key). So in a nutshell, those chords sound “good” to our ears in that key. Our musical brains are just programmed that way, from a very early age!
Of course there are exceptions, some of them quite wonderful. For example, what made the Beatles music so refreshing and different was that they very subtly altered a chord or two in certain songs, making our ears go – whoa, what was that?! In the beautiful John Lennon song “In My Life” the chords begin totally within the scale but then suddenly a minor is substituted for the Major IV chord. The change is only one note, a flatted 3rd, but it adds a new “color” to the song. Shortly after that a Major chord is substituted for the minor II. But in each case, those subtle changes are immediately resolved on the next change with a scale-line chord, making our ears go, ahhh….that’s nice! Pure genius in pop music and quite revolutionary at the time. Did John think that through? Who knows, but I’ll bet their legendary producer George Martin had something to do with it.
The challenge for the songwriter in popular music is to insert small changes, but nothing too jarring. The more notes that are outside the Major key that are found in chords, the more they sound strange to anyone who only listens to pop music. This is why many people find jazz quite challenging. In modern jazz the conventions of the Major Diatonic Scale and the matching chords are often abandoned entirely. This is why many advanced players love jazz, though. The rule book is thrown away and the doors to creativity are thrown wide open.
But for most music lovers and many guitar players, sticking to the tried-and-true is much more pleasing. There is nothing wrong with this! Take some time to examine the songs you play and make note of the chords that are used. You may even use this scale-line triad concept to begin writing songs of your own. But keep an open mind – and open ears.
Peace & good music,