Craft a musical piece that abides by the prescribed structural guidelines and the given theme.
X:1
L:1/8
M:3/4
K:D
['B,2 D4 D2 B,4 D<B, ||[M:4/4] B,E,', 'G,<E, D,4 B,,4 ||[M:3/4] B,,6 [M:4/4] D,4', 'D,B,, B,,3', 'B,,4 B,,6'  
X:1
L:1/8
M:3/4
K:D
 B,2 | D4 D2 | B,4 D<B, ||[M:4/4] B,E, E,<D,- D,2 G,<E, | D,4 B,,4 ||[M:3/4] B,,6 || 
[M:4/4] D,4 B,,2 D,B,, | B,,3 B,, B,,4 | B,,6 z2 |]  