An instrumental genre dedicated to dance with moderately tempo, reng possesses no other feature. Mostly composed in 6/8 meter, rengs are occasionally composed in other light-hearted measures. rengs in radif are more elaborated and less dance-like in character. Some musicians, like Ali-Akbar Shahnazi, composed numerous rengs.
Source: An Introduction to Iraninan music booklet from Mahoor Institute of Culture and Art