Compose a piece of music that follows the specified structure and incorporates the given theme.
X:1
L:1/4
M:4/4
K:Bb
['D D']  
X:1
L:1/4
M:4/4
K:Bb
 z2 z D | D D D D | D D D D | F E D D | d3 d | c B A c | B A G B | A G F E | D3 z |]  