The unusual sounds shed light on the ancient mystery: What Does the Fox Say?
The plaintext consists of Ylvis's proposals for what the fox may say:
The plaintext has been encrypted using a substitution cipher. The ciphertext has been written in Morse code (since the fox, meeting a friendly horse, may communicate in Mo-o-o-o-orse). The hyphen (-....-) and exclamation point (-.-.--) have also been encoded, and all inter-element gaps between letters have been removed (the space between “A-hee-ahee” and “ha-hee” has been left in).
Once you have realized the manner in which the cipher text comes from the song, it is possible to deduce the substitution key. For instance, the next-to-last line tells you what stand for “a” and “o,” and then these can be used to make other deductions. The whole key can be deduced in this manner except that the letters “i” and “n” always occur in the plaintext together as “in,” which encodes as “---..” There are four ways to split this up.
- / --.. = T/Z
-- / -.. = M/D
--- / .. = O/I
---. / . = [no letter]/E
But by this point you will have found that T,Z,O,I,E are already used in the cipher alphabet, so we must have plaintext i = ciphertext M and plaintext n = ciphertext D. The full substitution key, ordered by plaintext letter, is as follows.
abcdefghijklmnopqrstuvwxyz [plaintext] H*ARKZUBMIT**DEC*O*Y**S*** [ciphertext]
The answer is DECOYS.