Develop a musical piece incorporating the designated alphabet-based pattern and the supplied melodic theme.
X:1
L:1/8
M:4/4
K:F
['AG F2', 'c2 c2']  
X:1
L:1/8
M:4/4
K:F
 AG | F2 F2 FGAB | c2 c2 d2 dc | c2 A2 AG F2 | G4 F2 :| AB | c2 c2 cBAB | c2 c2 d2 d2 | 
 c2 A2 AG F2 | G2 GB !fermata!A2 AG | F2 F2 FGAB | c2 c2 d2 dc | c2 A2 AG F2 | G4 F2 |]  