Craft a musical composition that adheres to the specified musical theme and letter-based structure.
X:1
L:1/8
M:4/4
K:C
['DG G2 DGBd g2', 'gd (3Bcd g2 z f']  
X:1
L:1/8
M:4/4
K:C
[M:4/4][K:G]O Be!p!!p![Q:1/8=180] .Tz G | DG G2 DGBd | g2 z g (3efg dB | A2 A2 A2 BA | G2 AF GFEF | 
 DG G2 DGBd | g2 dg egdB | GABd gedc | (3Bcd AF G2 :| Bc | d2 gf gd (3Bcd | g2 z f gfed | 
 eaag a2 ag | eaag edBc | dggf gd (3Bcd | g2 z f gedB | GA (3Bcd gedc | BdAF G2 :|  