Craft a musical composition that adheres to the specified musical theme and letter-based structure.
X:1
L:1/8
Q:1/4=120
M:4/4
K:Bb
['vF2 uF>uG', 'B e (d<f)(f>g) (fg/a/) ub>ud c>Bd>B c>BG>e']  
X:1
L:1/8
Q:1/4=120
M:4/4
K:Bb
"^Strathspey." uG | vF2 uF>uG vF>vGuB>ud | vc>vBud>uB vc>uB(G<B) | vF2 uF>uG F>GB>g | 
 vf<Bve>ud c2 B :: e | (d<f)(f>g) (fg/a/) ub>ud | c>Bd>B c>BG>e |1 (d<f)(f>g) (f/g/a) ub>ud | 
 c>Be>d c2 B :|2 F>BD>B F>GB>g | f<B e>d c2 B |]  