Craft a musical composition that adheres to the specified musical theme and letter-based structure.
X:1
L:1/4
M:4/4
K:Eb
['c3/2 A/']  
X:1
L:1/4
M:4/4
K:Eb
 B B e3/2 B/ | G A B2 | B =B c f | e2 d2 | e3/2 c/ =B G | e3/2 c/ c =B | c3/2 A/ G C | 
 c3/2 A/ A G | c3/2 A/ G C | c3/2 A/ A G | F G A =A | B3/2 c/ B2 | =B c d e | E2 G3/2 F/ | E3 z |]  