Develop a musical composition by integrating the alphabetically represented musical pattern and the supplied melodic theme.
X:1
L:1/4
Q:1/4=120
M:6/4
K:Dmix
['d3/2 e/ f']  
X:1
L:1/4
Q:1/4=120
M:6/4
K:Dmix
 A | d3/2 e/ f d3/2 e/ f | (d3 d2) A | d3/2 e/ f d3/2 e/ f | (d3 d2) e | f2 e d2 c | B3 A3 | 
 A2 F A2 G | F3 F2 G | A2 A B2 A | d2 D F2 G | A3/2 G/ F E2 D | D3 F2 G | A2 A B2 A | d2 D F2 G | 
 A3/2 G/ F E2 D | (D3 D2) |]  