A tuna is a group of university students that sings traditional songs. Each section of the university (Law, Medicine, History, Architecture) has its own group. On the night of December 8, the feast of the Immaculate Conception of Mary, the tunas meet in the plaza of the Virgen de los Reyes, between Seville's cathedral and alcazar, to sing and make offerings in praise of the Virgin Mary.
Afterward, the groups stroll through the old quarter, singing, stopping often for tapas and beer, and flirting with girls.
Don't miss the tambourine guy's antics at the end.
By the way, tuna in Spanish is atún.