This song provides vertical strategies for hearing non-dominant 7ths. (Major 7 and minor 7 chords.) The melody often points out the seventh in the underlying harmony, and the lyrics address a strategy to hear the inversion of the seventh interval, which is a second. The guitar line helps highlight this in the chorus.
Let's start with a simple progression
Like a I chord, a ii and a IV.
Then let some sevenths and a passing chord spice up the score.
Then back to the place where we started...
The harmony pretty but plain.
Then add back those sevenths and make our way to the refrain.
Non-dominant sevenths, how you tickle my ear
In inversion your seconds are not so hard to hear
Non-dominant sevenths, nothing else can compare
And you may come and go, but I always will know when you're there.
When triads are minor or major
There's nothing unusual to hear
So when chords get more crunchy, it could mean a seventh is near
Without them the world has less color
It's pleasant, but sometimes it's bland.
When I hear a seventh, it makes things exciting and grand.
Even chromatic mediants can have a seventh to share
Oh, dear sevenths, I'm grateful to know even when your world modulates,
Sevenths may always be there!
Because of the chords they're attached to,
You often may hear them around.
They don't add much function, so you just have to know how they sound.
So study chords with and without them
Hear the root and what lies just below...
Then listen and practice, so when there's a seventh, you'll know!