Utilizing the provided musical theme and letter-based structure, compose a piece of music.
X:1
L:1/8
M:4/4
K:A
['AB cB', 'a2 AB cd e2 dc Bc de']  
X:1
L:1/8
M:4/4
K:A
|: [EA]G AB cB AB | Aa ga (3faf e2 | AG AB cB Ac | [GB]B [EB]B [GB]B [EB]B | AG AB cB AB | 
 Aa ga (3faf e2 | GB ed cB AG | A2 a2 :: AB cd e2 dc | Bc de f2 ed | ce fg a2 gf | ea gf ed cB | 
 Aa ga fd BG | A2 a2 :|  