The Case of the "Flitterbat Lancers"

"The meaning of the thing was so very plain," Hewitt said to me / afterwards, "that the duffers who had the ‘Flitterbat Lancers' in / hand for so long never saw it at all. If Shiels had made an ordinary / clumsy cryptogram, all letters and figures, they would have seen what / it was at once, and at least would have tried to read it; but because / it was put in the form of music, they tried everything else but the / right way. It was a clever dodge of Shiels's, without a doubt. Very / few people, police officers or not, turning over a heap of old music, / would notice or feel suspicious of that little slip among the rest. / But once one sees it is a cryptogram (and the absence of bar-lines / and of notes beyond the stave would suggest that) the reading is as / easy as possible. For my part I tried it as a cryptogram at once. You / know the plan -- it has been described a hundred times.

See here -- look / at this copy of the ‘Flitterbat Lancers.' Its only difficulty -- and / that is a small one -- is that the words are not divided. Since there / are on the stave positions for less than a dozen notes, and there are / twenty-six letters to be indicated, it follows that crotchets, / quavers, and semiquavers on the same line or space must mean / different letters. The first step is obvious. We count the notes to / ascertain which sign occurs most frequently, and we find that the / crotchet in the top space is the sign required -- it occurs no less / than eleven times. Now the letter most frequently occurring in an / ordinary sentence of English is _e_. Let us then suppose that this / represents _e_. At once a coincidence strikes us. In ordinary musical / notation in the treble clef the note occupying the top space would be / E. Let us remember that presently.