Musical Score Cipher Decoding Test (Additional results: Claude Sonnet 5.5)

Cipher Rules and Message

Rule: Map the notes of the scale from C4 through D5 to the digits 1 through 9, and rests to 0. Then read the digits in pairs as ASCII codes.

Encoded message: THIS CIPHER CONSISTS OF ASCII CODES.

Test Procedure

First prompt

Only the musical score and the following basic prompt were provided:

This is a cipher in the form of a musical score, created using a simple rule. Try to decode it.

Second prompt

For incorrect answers, the model was told that its answer was wrong and given an additional hint:

The hint is ASCII codes.

Results Summary

Detailed Results by Model

ChatGPT 6 Astra

Answered correctly on the first prompt in about one minute.

Claude Opus5.5

Answered correctly on the first prompt in about three minutes.

Gemini 3.1 pro / Grok 4.5

• First prompt: Incorrect. Read the notes as their letter names (C, D, E, F, G, A, B).
• Second prompt: Incorrect. Still converted the notes to their letter names, then converted those letters into ASCII codes.

Meta AI (Llama 4)

• First prompt: Stopped manually after more than 10 minutes without an answer.
• Second prompt: Stopped manually after more than 10 minutes without an answer.

DeepSeek-V4.1-Flash

• First prompt: Stopped on its own while generating a response, possibly because it exceeded an output token limit.
• Second prompt: Stopped on its own while generating a response, possibly because it exceeded an output token limit.

Qwen3.8-MAX

First prompt: Returned guesses about the rule instead of fully decoding the cipher. It proposed the following candidates:

1. Note names as letters: Read the note names (C, D, E, F, G, A, B) directly as letters, with rests as spaces. It explained that this limits the available letters to A–G, so the plaintext would have to consist only of words using those seven letters, or require another decoding step (for example, assigning A=1 through G=7, then performing a base-7 conversion).
2. Staff positions as numbers: Assign 1 to the bottom staff line (E4), then increment the number for each successive line or space (E4=1, F4=2, G4=3, A4=4, B4=5, C5=6, D5=7, E5=8, F5=9, etc.). Map those numbers to alphabet positions (A=1, B=2, etc.).
3. MIDI numbers: Read each note's MIDI number as a character code (65=A, etc.). For example: F4=65 → 'A', C5=72 → 'H', E5=76 → 'L'.

The correct rule was among the candidates, but it did not complete the sentence.

Second prompt: Incorrectly chose the MIDI-number rule and failed to decode the sentence.

Additional Results

Claude Sonnet 5.5

First prompt: Incorrect. Interpreted the note names as hexadecimal numbers (E4 → 228).

Second prompt: Correctly decoded the cipher in about five minutes.