Craft a musical composition that adheres to the specified musical theme and letter-based structure.
X:1
L:1/8
M:4/4
K:D
['AF F2', 'defg abag']  
X:1
L:1/8
M:4/4
K:D
"^reel" AF F2 AFdB | AF F2 BE E2 | AF F2 AFdF | D3 E FD D2 :| defg abag | fded fdBc | defg abag | 
 fdec d2 d2 | defg abag | fded fdBc | defg abag | fdec Ad d2 |]  