Around 1900 plena emerged as a humble proletarian folk genre in the lower-class, largely Afro-Puerto Rican urban neighborhoods in San Juan, Ponce, and elsewhere. Plena subsequently came to occupy its niche in island music culture. In its quintessential form, plena is an informal, unpretentious, simple folk-song genre, in which alternating verses and refrains are sung to the accompaniment of round, often homemade frame drums called "panderetas" (like tambourines without jingles), perhaps supplemented by accordion, guitar, or whatever other instruments might be handy. An advantage of the percussion arrangement is its portability, contributing to the plena's spontaneous appearance at social gatherings. Other instruments commonly heard in plena music are the cuatro, the maracas, and accordions.