Craft a musical composition that adheres to the specified musical theme and letter-based structure.
X:1
L:1/8
M:6/8
K:C
['dcd fed A2 d', 'FAA AFD GBB BAG']  
X:1
L:1/8
M:6/8
K:C
 B | Add dcd | fed A2 d | Bee edc | Bee cBA | Bdd dcd | fed A2 d | Bdd cBc | d2 d :| A/G/ | 
 FAA AFD | GBB BAG | Acc cBc | dcd BAG | FAA AFD | GBB BAG | d2 d :|  