Craft a musical composition that adheres to the specified musical theme and letter-based structure.
X:1
L:1/8
M:4/4
K:D
['dD (3DDD DEFA', 'd2 fd Adfd']  
X:1
L:1/8
M:4/4
K:D
 dD (3DDD DEFA | dfaf gfec | dD (3DDD DEFA | BdAF EDB,D | dD (3DDD DEFA | dfaf gfec | Addc dAFA | 
 GFEF GABc || d2 fd Adfd | (3ddd fd BAFA | d2 fd Adfd | BdAF EDB,D | d2 fd Adfd | Adef gefg | 
 afge faec | dBAF GABc | d2 fd Adfd | (3ddd fd BAFA | d2 fd Adfd | BdAF EDB,D | a3 b afef | 
 gfef g2 fe | faec dBAF | GFEF GABc ||  