Craft a musical piece that abides by the prescribed structural guidelines and the given theme.
X:1
L:1/8
Q:3/8=90
M:6/8
K:A
['a3 c2 d']  
X:1
L:1/8
Q:3/8=90
M:6/8
K:A
 e3{g} a3 | c2 d ecA | BGE BGE | ecA BGE | e3 a3 | c2 d efg | agf gab | Be^d e3 |:  