A man in a black shirt is holding a guitar.
A musician is holding an instrument.
If holding an instrument makes you a musician, a man holding a guitar therefore can be a musician.
exists e1 s1 x1 x2 x3.(Theme(e1,x3) & Actor(e1,x1) & v_hold(e1) & n_guitar(x3) & in(x1,x2) & n_shirt(x2) & a_black(s1) & Theme(s1,x2) & n_man(x1))
exists e1 x1 x2.(Theme(e1,x2) & Actor(e1,x1) & v_hold(e1) & n_instrument(x2) & n_musician(x1))