Design a musical composition incorporating the alphabetic expression of the chosen structure and the provided melodic theme.
X:1
L:1/16
M:2/4
K:G
['GBdB cdef', '[B,G]2 .d2(Bc) .d2.g2 fafd ege^c .d2(B=c) .d2.g2']  
X:1
L:1/16
M:2/4
K:G
 (3DEF | GBAG GBdB | cdef gedB | G2(BA) GBdB | ABAG FDFA | G2(BA) GBdB | cdef (3ggg(dB) | 
 edce dBGB | AGFA [B,G]2 :: .d2(Bc) .d2.g2 | fafd ege^c | .d2(B=c) .d2.g2 | fge^c d2>e2 | 
 defe dcBA | .B2(AG) BGEF | .G2(DE) .G2.e2 | dBcA G2 z2 :|  