Compose a piece of music that follows both the given musical theme and the letter-based structure provided.
X:1
L:1/8
M:6/8
K:Bb
['(dfb) (fdB) (GcB) (ABc) (Bcd) (efg)', 'e2 d (dcB)', 'd2 d2', 'G2 G2']  
X:1
L:1/8
M:6/8
K:Bb
 (f/e/) | (dfb) (fdB) | (GcB) (ABc) | (Bcd) (efg) | (fdB) (AGF) | (dfb) (fdB) | (GcB) (ABc) | 
 (Bcd) (efg) |1 (de)c B2 :|2 (dec) B3 |: e2 d (dcB) | e2 d (dcB) | (Gc)c c2 B | (Ac)c c2 d | 
{f} e2 d (dcB) |{f} e2 d (dcB) | (Gc).c c2 B | ABc B3 :|[M:4/4][K:G] (Bc)(dB) G2 (gf) | 
 e2 (ag) (fd)(ef) | (gf)(gd) (cA)(BG) | F2 A2 A2 z2 | (Bc)(dB) G2 (gf) | e2 (ag) f2 (ba) | 
 (gf)(ge) (fd)(e^c) | d2 d2 d2 z2 |] (fg)(af) d2 (ef) | (ga)(bg) d2 (Bd) | (dc)(Ac) (cB)(GB) | 
({B} A^G)(AB) | (AD)(EF) | (GA)(BG) (EFG^G) | (AB)(cA) (FGA^A) | (Bc)(dB)({d} cB)(cA) | 
 G2 G2 G2 z2 |]  