Three members of a band are all practicing their different instrument skills.
Some musicians are practicing their various instruments.
Musicians can be members of a band.  Various and different have the same meaning.
exists e1 s1 x1 x2 x3 x4 x5 x6.(n_skill(x5) & of(x5,x6) & n_instrument(x6) & a_all(s1) & Manner(e1,s1) & Theme(e1,x3) & Actor(e1,x1) & v_practice(e1) & -(x3 = x5) & n_skill(x3) & of(x3,x4) & n_instrument(x4) & of(x3,x1) & n_thing(x1) & of(x1,x2) & n_band(x2) & n_member(x1) & card_eq_3(x1))
exists e1 s1 x1 x2.(Theme(e1,x2) & Actor(e1,x1) & v_practice(e1) & n_instrument(x2) & a_various(s1) & Theme(s1,x2) & of(x2,x1) & n_thing(x1) & n_musician(x1))