Two people are playing guitar, while a third is flaying the drums.
The people are at a rock concert.
There are other kinds of concerts that may use those instruments aside from a rock concert.
exists e1 p1 x1 x2 x4.(n_drum(x4) & exists e2 x3.(Theme(e2,x4) & Actor(e2,x3) & v_flay(e2) & n_third(x3)) & while(e1,p1) & Theme(e1,x2) & Actor(e1,x1) & v_play(e1) & n_guitar(x2) & n_people(x1) & card_eq_2(x1))
exists p1 x1.(n_people(x1) & exists x2 x3.(at(x1,x2) & n_concert(x2) & of(x2,x3) & n_rock(x3)))