Complex sentence: They also began decreasing music from the pre 1964 era, eventually all the pre 1964 oldies were eliminated and a lot of 1980s music were added to the mix, becoming more of a classic hits station.
Split into simpler sentences: They also began decreasing music from the pre 1964 era. They later completely eliminated all the pre 1964 oldies and added a lot of 1980s music to the mix, becoming more of a classic hits station.