Craft a musical piece that abides by the prescribed structural guidelines and the given theme.
X:1
L:1/8
M:4/4
K:G
['BGcA defg', 'g2 bg f2 af e2 ge dcBd'  
X:1
L:1/8
M:4/4
K:G
 BGcA defg | G2 BG AFDc | BGcA defg | dBcA G3 c | BGcA defg | G2 BG AFDc | BGcA defg | dBcA G3 d || 
 g2 bg f2 af | e2 ge dcBd | c2 ec B2 dB | AGAB cdef | g2 bg f2 af | e2 ge dcBd | cdec B2 dB | 
 AGFA | G2 ||  