Develop a musical piece incorporating the designated alphabet-based pattern and the supplied melodic theme.
X:1
L:1/8
M:6/8
K:G
['GAB ABc']  
X:1
L:1/8
M:6/8
K:G
 d |"G" B>AB"Em" GAB |"Am" c>Bc"D7" ABc |"G" BAB"Em" GAB |"D7" AFD D2 c |"G" BAB"Em" GAB | 
"Am" cBc"D7" ABc |"G" B{c}dB"D7" cAF |"G" G3 G2 :: f |"G" gbg"Em" gbg |"Am" ac'a"D7" ac'a | 
"G" gbg"Em" gbg |"D7" afd d2 f |"G" gbg"Em" gbg |"Am" ac'a"D7" abc' |"G" bag"D7" agf |"G" g3 g2 :|  