Definition: Common time (also “imperfect time”) refers to the 4/4 time signature, which signifies four quarter-note beats per measure. It may be written as a fraction, or with a c-shaped semicircle. If this symbol has a vertical strikethrough, it’s known as “cut common time.”
Origins of the Common Time Semicircle
The c-shaped symbol representing 4/4 time is often mistaken as an abbreviation for ‘common time.’ But, however appropriate, its origins are a bit more divine in nature.
When modern notation was in its first stages of development, both the complete circle and the number 3 were regarded as perfect – the circle because of its infinite line, and 3 because it represented the Holy Trinity. This led to triple meter (also called “perfect time”) being represented by the circle, while imperfect time – a type of quadruple meter – was written using an incomplete, “imperfect” circle.1
1 Write it Right! [pg. 12]: Dan Fox. Published by Alfred Publishing Co., 1995.