A string fixed at both ends keeps only the voices that fit: a whole count of half-waves, nothing else. Pluck it and every allowed voice sounds at once — then the high ones, with farther to travel, die first, and the chord pares itself down to the fundamental.
Drag across the string and release to pluck it. Sweep the slider to isolate one harmonic and watch its nodes stand still. Pluck sounds the chord; voice sounds the isolated harmonic alone.