Scale tone chords.
There are 7 notes in a scale. In the key of C major its, c,d,e,f,g,a,b. in any major key the progression goes, tone, tone, semitone, tone,tone,tone, semitone.
That's the notes. For the chords the progression is, I major, II minor, III minor, IV major, V major, VI minor, VII diminished.
In a key of C major the scale tone chords are C major, D minor, E minor, F major, G major, A minor, B diminished.
At this point I'm hoping those chords are familiar to everyone. There are millions of songs in the key of C which only use the chords C major, F major and G major. Progressions using only those 3 chords or in any key, I major, IV major and V major aren't copyrightable.
The example given may be from a song that's so old and out of copyright that its technically correct but as examples go its still bonkers.
Anthony
