Complex sentence: Starting in the 1920s as WHN it played a diversified format, it was renamed WMGM in the late 1940s, the diversity continued until a switch to rock & roll in the late 1950s and early 1960s.
Split into simpler sentences: Starting in the 1920s as WHN, it played a diversified format. It was renamed WMGM in the late 1940s, continuing the same format until a switch to rock & roll in the late 1950s and early 1960s.