Develop a musical piece that combines the given theme and letter-structured outline.
X:1
L:1/8
M:4/4
K:D
['fg a2 gbag fefa gfef', 'defg a2 gbag', 'gfef dcde fdec AGFG ABcA dcAG ABcA']  
X:1
L:1/8
M:4/4
K:D
 fg |:"D" a2 af"G" gbag |"D" fefa gfef |"D" dcde fdec | dedc"G" AGFG | ABcB dcAG | 
"D" FEFG"A" ABcA |"D" dcdf"A" edce |1"D" d2 dd defg :|2"D" d2 dc d2 |: A2 | dcde fefg | 
"A" a2 af"D" defg |"A" a2 af"D" gbag | f2 fe defg |"A" a2 af"D" gbag |"D" fefa"D" gfef | 
 dcde fdec | dedc"G" A2 fg |"A" a2 af"D" gbag |"D" fefa"D" gfef | dcde fdec | dedc"G" AGFG | 
"A" ABcA dcAG |"D" FEFG"A" ABcA |"D" dcdf"G" edce |1"D" d2 dc d2 :|  