SANTIAGO, Chile — Lollapalooza Chile has introduced me to a world-class party band: Chico Trujillo, a local favorite who had a huge crowd shouting along. Every party band needs a rhythm, and Aldo Asenjo, the band’s leader and singer, relies on cumbia, the beat heard in countless variations across Latin America. Cumbia often trots calmly, but Chico Trujillo’s version gallops, bounding along; now and then, the music switches into rumba, equally upbeat. Mr. Asenjo sings lyrics as chattery and percussive as some hip-hop, taking on the ups and downs of love and life, with his voice answered by chortling horns — did he borrow the arranging idea from ska bands? — and a tootling, circusy organ. Syncopation, momentum and a way of romping through pain — a party band needs them all, and Chico Trujillo has them.