Develop a musical piece incorporating the designated alphabet-based pattern and the supplied melodic theme.
X:1
L:1/8
M:2/4
K:none
['', 'ca Bg g/d/B/G/ Fe', 'gc df/e/']  
X:1
L:1/8
M:2/4
K:none
[K:G] B"_c"c |: dB"_c" ca | Bg g/d/B/G/ | Fe e/d/"_c"c/A/ | G/B/d/g/ bB/"_c"c/ | db"_c" ca | 
 Bg g/d/B/G/ | Fe e/d/"_c"c/A/ |1 GB GB/"_c"c/ :|2 GB G z ||[K:D] A>B A>B | Af f2 | fe gc | 
 df/e/ dd | A>B A>B | Af f2 | fe gc | df/e/ d2 |]  