Utilizing the provided musical theme and letter-based structure, compose a piece of music.
X:1
L:1/8
M:2/4
K:none
['[K:D] .A.A .A.A AB AG G/F/E GF', 'AD/D/ DD d>d cB', 'A3 G']  
X:1
L:1/8
M:2/4
K:none
[K:D] .A.A .A.A | AB !>!B2 | AG G/F/E | GF F/E/D | AA AA | Ac !>!c2 | B/A/G G/F/E | AE FG :| 
 !>!A2 !>!B2 | G"_=CC"E/E/ EE | !>!B2 !>!c2 | AD/D/ DD | d>d cB | A>A GF | E/F/G G/F/E | F/G/A A2 | 
 !>!A2 !>!B2 | GC/C/ CC | !>!B2 !>!c2 | AD/D/ DD | d>d cB | BA A/G/F | A/G/A/G/ FE | DF D z |: 
[K:G] B3 A | G3 F | EA AA | A3 z | A3 G | F3 E | DG GG | G3 z | d3 B | A3 G | E"_c"c cc | c3 B | 
 AD AD | BG e>d |"_c" cF B>A | GB G z :|  