This paper examines the social aesthetics of reng, a precomposed instrumental form in Iranian dastgāh music, and its gradual decline since the late twentieth century. Historically associated with dance (raqs), reng functions as a lively piece in duple or triple meter at moderate to fast tempos in Persian classical music (Farhat 2004, 22). For centuries, reng’s connection to dance embodiment, courtesan culture, and theatrical entertainment contributed to its lower artistic status under Islamic rule. During the early twentieth century, however, the modernist reforms of the Pahlavi era and new developments of Iranian art music elevated both the musical complexity and cultural standing of reng. It emerged as a respected independent composition, valued for rhythmic vitality and stylized syncopation, and frequently concluded prominent vocal genres such as tasnīf or an entire dastgāh performance (Azadehfar 2011; Zonis 1973). The compositional innovations of master-musicians, including Ali-Naqi Vaziri, Abolhassan Saba, Ruhollah Khaleqi, Darvishkhan, and Faramarz Payvar, further consolidated its pedagogical and performative significance. Despite these developments, reng entered a new phase of decline in the late twentieth century. Through analysis of selected musical examples, this study traces this fading to broader socio-cultural transformations: emergent waves of traditionalisms enhanced by orientalist discourses of spirituality, the marginalization of the popular 6/8 idiom (shish-o-hasht), and cultural reforms intensified after the 1979 revolution. I argue that shifts in social aesthetics, embodied ideologies, and reconfigured identities have decisively shaped the fortunes of reng in contemporary Iran. This study contributes to the broader debates on music, aesthetics, and cultural transformation.