In Vivo, each round starts by revealing a harmony type (Solo, Duet, Trio, Quartet). The harmony determines how many suits must be played in the trick—not being able to is considered playing “off-harmony,” making that player ineligible for points.
At the end of the trick, the player who played the highest on-harmony card scores two points, and the lowest on-harmony card scores for the value of that card (those bass notes are so important!).