Craft a musical composition that adheres to the specified musical theme and letter-based structure.
X:1
L:1/8
Q:1/8=150
M:2/2
K:D
['dB AFDF AFdB A2 FA fedc BABf', 'de fdcd BdAF Ddcd fdcd']  
X:1
L:1/8
Q:1/8=150
M:2/2
K:D
 dB | AFDF AFdB | A2 FA fedc | BABf gefd | edcB A2 dB | AFDF AFdB | A2 FA fedc | BABf gefd | 
 ecAc d2 :| de | fdcd BdAF | Ddcd fdcd | eA A2 fA A2 | e2 dB A2 de | fdcd BdAF | Ddcd fdcd | 
 eAfA gAfA | ecAc d2 :|  