From Guitar World Holiday 2019
String Theory by Jimmy Brown
Using the “four minor” chord in a major key
Jimmy Brown continues the discussion an intriguing type of chord change that many composers have put to great use in countless major-key songs. It involves “borrowing” a chord from what’s called the parallel minor key to create a temporary harmonic detour and a surprise shift in musical color and mood that’s often used to impart a touch of sadness or melancholy to an otherwise happy -and predictable- sounding progression.
Here, Jimmy references some pretty well-known examples of this practice, starting with the use of the most widely borrowed chord in popular music, “four minor.”