Utilizing the provided musical theme and letter-based structure, compose a piece of music.
X:1
L:1/8
M:4/4
K:D
['d2 fd', 'fg aAA/A/A aAgA aAA/A/A gfga bBB/B/B bBaB']  
X:1
L:1/8
M:4/4
K:D
 d2 fd egfe | defd g2 fe | d2 fd efge | fgaf bgfe | d2 fd egfe | defd a2 fe | d2 fd efge | 
 abaf g2 fg || aAA/A/A aAgA | aAA/A/A gfga | bBB/B/B bBaB | bBB/B/B/ g2 fg | aAA/A/A aAgA | 
 aAA/A/A gfga | bBB/B/B bBaB | ABdf gfef ||  