Develop a musical piece using the given theme and incorporating the letter-based structure provided.
X:1
L:1/8
Q:3/8=88
M:6/8
K:D
['d>ed def gfe afd d>ed e2 f', 'f2 d e2 a', 'd3 a>ba afd g>ag gec d>ed e2', 'F2 A G2']  
X:1
L:1/8
Q:3/8=88
M:6/8
K:D
 d>ed def | gfe afd | d>ed e2 f | gec d3 :| f2 d e2 a | f2 d e2 a | d>ed e2 f | gec d3 :| 
 a>ba afd | g>ag gec | d>ed e2 f | gec d3 :| F2 A G2 B | A2 c d2 d | F2 A G2 f | gec d3 :|  