People say the Beatles were masters of harmony. But what does that mean? It means they knew how to craft amazing chord progressions -- combining chords in unexpected, but satisfying, ways that made their songs great. And they often did this using a technique called "modal mixture." Here's an excellent example....
https://youtube.com/live/vEAUqygOuKg
To dive into the details yourself, here are the diagrams we explored in the video: