Design a musical composition incorporating the alphabetic expression of the chosen structure and the provided melodic theme.
X:1
L:1/8
M:4/4
K:C
['def AFA', 'Add fdB']  
X:1
L:1/8
M:4/4
K:C
 |[M:6/8][K:D] (3:2:1TA | def AFA | DED AFA | def AFA | EFA TB2 A | def AFA | DED AFA | dcB AGF | 
 EFA TB2 :| A | Add fdB | cBc ecA | Add fdB | AFA{A} B2 A |1 Add fdB | cBc efg | fdB AGF | 
 EFA B2 :|2 Aff fed | cee efg | fdB AGF | EFA B2 |]  