Craft a musical composition that adheres to the specified musical theme and letter-based structure.
X:1
L:1/8
M:9/8
K:Dmix
['F3 AFE F3 AFD E3', 'B2 ABdA B2']  
X:1
L:1/8
M:9/8
K:Dmix
 F3 AFE | F3 AFD | E3 FED | E3 FED | F3 AFE | F3 AFD | E3 FEF | D6 | F3 AFE | F3 AFD | E3 FED | 
 E3 FED | F3 AFE | F3 AFD | E3 FEF D3 EFA |: B2 ABdA | B2 AFED | F3 AFE | F3 AFD | B2 ABdA | 
 B2 AFEF | D3 FEF | D6 :|  