Even to the untrained ear, the difference between these two recordings is plain. First is the change in her voice itself, which grew deeper and physically matured as she aged, reflecting what happens in most people as we get older. But there are other, more subtle shifts that can be charted in the decades' worth of recordings of the Queen. They are allowing scientists to understand the way in which accents evolve over time, and how they can be influenced by social, cultural and technological developments.
