Síncopa 3-3-2 — the other half of tango rhythm. Where marcato walks in four, the síncopa divides the bar into three-plus-three-plus-two eighths: hits on 1, the and of 2, and 4. In Piazzolla's nuevo tango it becomes a driving ostinato (the Libertango bass); in traditional orquestas it alternates with marcato bars.
How it sits: piano plays the chord in both hands on the three hits, the first accented; the clave layer shows the bare 3-3-2 so you can loop it alone. The bass follows the same rhythm, root–root–fifth. It is the three-three-two cell, the same grouping as the tresillo, but played heavy and on the beat rather than as a Caribbean syncopation — tango stresses the arrival on 4.
Listen for the chord on 4 being short: it closes the bar instead of leaning into the next one.
Practice: alternate one bar of this with one bar of marcato in 4 and keep the quarter-note pulse identical across the switch.