G, also called Sol or So, is the fifth note of the fixed-do solfège starting on C. It is the fifth note and the eighth semitone of the solfège. As such it is the dominant, a perfect fifth above C or perfect fourth below C.
When calculated in equal temperament with a reference of A above middle C as 440 Hz, the frequency of middle G (G4) note is approximately 391.995 Hz. See pitch for a discussion of historical variations in frequency.