Hello Jeffery,
this code should do approximately what you described.
toHalfTones[ note_] :=
Module[{octave = ToExpression[StringTake[note, -1]],
pitch = StringDrop[note, -1],
lst1 = {"C" -> 0, "C#" -> 1, "D" -> 2, "D#" -> 3, "E" -> 4,
"E#" -> 5, "F" -> 5, "F#" -> 6, "G" -> 7, "G#" -> 8, "A" -> 9,
"A#" -> 10, "B" -> 11, "B#" -> 12}},
12 (octave - 4) + (pitch /. lst1)]
sn10 = Map[{Round[#[[2]], 0.15], {toHalfTones[#[[1]]], #[[4, 2]]}} &,
sn[[2]]]
Please check, I am not an expert on the proper notation of music