People watch a musician play the guitar.
A guitarist practices alone.
A guitarist is a form of a musician.
exists e1 s1 x1 x2 x3.(Theme(e1,x2) & Actor(e1,x1) & v_watch(e1) & n_guitar(x3) & (x2 = x3) & n_play(x2) & a_musician(s1) & Theme(s1,x2) & n_people(x1))
exists x1 x2.(a_topic(x1) & r_alone(x1) & n_practice(x1) & of(x1,x2) & n_guitarist(x2))