Craft a musical composition that adheres to the specified musical theme and letter-based structure.
X:1
L:1/8
M:4/4
K:F
['FDCD FGAG FDCD FGAc cAdA cAFA', 'G2 F2']  
X:1
L:1/8
M:4/4
K:F
|: FDCD FGAG | FDCD FGAc | cAdA cAFA | G3 F G2 AG | FDCD FGAG | FDCD FGAc | cAdA cAFA |1 
 G2 F2 F3 G :|2 G2 F2 F2 Ac |: d3 f dcAB | c2 cd cAFA | B2 dB A2 GF | DGGF G3 A | FDCD FGAG | 
 FDCD FGAB | cAdA cAFA |1 G2 F2 F2 Ac :|2 G2 F2 F3 G ||  