Gregorian chants were some of the earliest forms of music used in religious ceremonies dating back to the Dark Ages. They were sung in Latin and followed specific musical notation for rhythms and pitches that differed from modern notation. Some of the unique notation included punctum, virga, podatus and other symbols to represent rhythms equivalent to 8th notes. The chants were mainly written in the keys of C, F, G for happier pieces and D, E, A for more somber pieces, though the key of B was thought to be forbidden and cursed.