Develop a musical piece using the given theme and incorporating the letter-based structure provided.
X:1
L:1/8
M:4/4
K:D
['dA A/A/A', 'B/c/d ef g2']  
X:1
L:1/8
M:4/4
K:D
 dA A/A/A dAFA | dA A/A/A g2 fe | dA A/A/A dAFA | G E3 GABc :| dcdf edcA | B/c/d ef g2 fe | 
 dcdf edcA | G E3 GABc | dcdf edcA | B/c/d ef g2 fg | abaf gfed | B/c/d ef g2 fe ||  