Compose tunes based on the given letter-based musical structure and the supplied motif.
X:1
L:1/16
M:2/4
K:F
['G A']  
X:1
L:1/16
M:2/4
K:F
 F2 G A F2 E D | c2 d f c4 | c2 d2 f2 c A | c2 G A G4 | c2 G A c E3 | D F G A F4 | F2 G A A2 F D | 
 C2 D F C4 |]  