The Beatles used the I-V-vi-IV chord progression most often in their songs. This four chord pattern is comprised of:
* I - The tonic, or root note of a key
* V - The dominant, which creates tension and leads back to the tonic
* vi - The relative minor, which adds variation and color to the progression
* IV - A subdominant that also returns to the tonic.
This simple yet powerful sequence can be found in many of their most memorable songs such as Hey Jude and Let It Be.