sentences:  AM 640 was originally a MOR station in 1990 when it signed on as WBMX, using the call sign that had recently been vacated by a popular urban contemporary station in Chicago, Illinois.The following year, the owners of WROR-FM 98.5 in Boston, Massachusetts, bought the WBMX call letters from 640 in order to debut "Mix 98.5" there; in return, AM 640 received the WROR calls.Its format did not change.