Well, in any major key (a pleasant reference pattern of tones), there are only seven different pitches (notes) and seven chords (each built from each pitch). These seven chords have three different sounding characteristics with three major, three minor and one diminished. Pop songs are short and repetitious by the likes of our ear/brain nature. Jazz bends things but when they do, the music is not so accessible and shifts reliance more on mood than pattern.
The three major chords are Louie Louie (aka I IV V). If you add a fourth chord, say the minor vi in this pattern I vi IV V, you have every Do Wop song ever recorded.
Keep in mind the rules of music (aka music theory, or music harmony) are not rules… they were not invented but discovered. It is what our ear/brain likes. Some day, all of the patterns that humans “like” will be discovered and published. These patterns can be chordal or single melodic. But, if you package them differently, you can have a new tune.
Sometimes writers blatantly steal like MC Hammer stealing Rick James… other times they just re-discovered a pattern innocently. The courts are fascinating place where this can play out.
Did George Harrison really steal He’s So Fine (aka My Sweet Lord) ? Probably not… but the courts made him write some checks anyway.
Peace
Bruce in Philly
