Griffin's Lullaby

Challenge Category: Miscellaneous

Points: 500 pts

Time spent: 1-2 hours

Tools required: Sonic Visualiser or Audacity (spectrogram), CyberChef (Vigenère Decode)

Description: Not every Griffin has wings; one of them wrote a lullaby for his son.

You got one file, Lullaby.mp3: about 75 seconds of piano playing Brahms’ Lullaby twice. The piano is not the message. A quiet flute plays underneath it, and the flags hide in the flute.

Step 0: Find the second instrument

Listen with headphones, or open the file in Sonic Visualiser or Audacity and switch to a spectrogram (log frequency, about 200–1000 Hz). The loud notes follow the lullaby. Under them, a fainter line of notes does not belong to the tune. It plays twice:

• 0:18–0:35, under the second half of the first time through
• 0:41–0:56, under the first half of the second time through

Tip: the piano part is identical both times, so compare the same spot in the two passes. Anything that shows up in one pass and not the other is the flute.

Step 1: Write down the notes

The flute plays one note per beat (80 BPM), and some beats are silent. Writing one note or rest per beat gives two lines:

Line 1: G#5 F4 B4 F5 D#5 rest C4 F#5 B3 G#4 E4 A#4 C#5 rest B4 A#5 B3 G#4 rest D4 F#4 A#5
Line 2: A3 F4 F#4 E5 G#4 F#5 A#3 rest A#4 F5 C#4 A4 E4 rest A#3 C5 rest E4 A5 A3

Step 2: Notes to letters

The flute stays between A3 and A#5: 26 half steps, one for each letter. Start at A3 (220 Hz) = A and count up one letter per half step:

A silent beat is an underscore:

Line 1: XIOUS_DVCLHNQ_OZCL_FJZ
Line 2: AIJTLVB_NUEMH_BP_HYA

Neither line reads as English, so there is a cipher on top. The description is a riddle that points to a word, so try Vigenère with that word as the key.

Step 3: The obvious key is a trap

The tune is Brahms’ Lullaby, so BRAHMS is the first key to try. Vigenère Decode in CyberChef, key BRAHMS, on line 1:

WRONG_LULLABY_NICE_TRY

tribectf{wrong_lullaby_nice_try} is a fake flag, and it says so. BRAHMS on line 2 gives junk.

Step 4: Find the right Griffin

Read the description again: “Not every Griffin has wings; one of them wrote a lullaby for his son.” This Griffin is not the W&M mascot, and the lullaby is not Brahms’ (he wrote his for a friend’s baby). It’s Merv Griffin, who created Jeopardy!. He wrote the show’s “Think!” music, the 30 seconds that play during Final Jeopardy, as a lullaby for his son Tony. It was first called “A Time for Tony”.

The key is JEOPARDY.

Step 5: Decrypt

Vigenère Decode, key JEOPARDY, on line 2. Underscores do not use up key letters, which is CyberChef’s default:

REVELEY_PLAYS_BY_EAR

Reveley is the name of W&M’s Griffin mascot.

Flag

tribectf{reveley_plays_by_ear}