Design a musical composition incorporating the alphabetic expression of the chosen structure and the provided melodic theme.
X:1
L:1/16
M:3/8
K:Bb
['BdfecA Bdfbag f4 f2 ^fgfgde', 'ABcAFA BcdBFB', 'f4 b2 f4 d2 c2ecA2']  
X:1
L:1/16
M:3/8
K:Bb
 F2 | BdfecA | BdfecA | Bdfbag | f4 f2 | ^fgfgde | (=Bc)(Bc)(de) | f^fgedc | B2A2F2 | 
 (Bd)(fe)(cA) | BdfecA | Bdfbag | f4 f2 | ^fgfgde | =BcBcde | f^fgecA | B4 || F2 | ABcAFA | 
 BcdBFB | cdecAc | d2fdB2 | ABcAFA | BcdBFB | cdecAc | B4 || f2 | f4 b2 | f4 d2 | c2ecA2 | B2B2f2 | 
 f4 b2 | f4 d2 | c2ecA2 | B4 ||  