Underrail – The Utter Pipeworker’s Guide to the Musical Cipher

Spoiler guide to getting the sonic gun in the Expedition DLC. Try it without a guide first, ya freeloader!

The Setup

I happen to like puzzles and ciphers, but you may not!

A straightforward walkthrough is of no help when it comes to unlocking the sonic gun – the code is randomized, so you’ll have to figure it out yourself.

Not only that, but I found the in-game description to be noooot all that great. It’s not that the clues aren’t there, it’s just that there is a lot of text to sort through, and most of the information isn’t particularly helpful.

So here: the Complete Pipeworker’s guide to the musical cipher!

Notes You Need

There are three notes you need to solve the musical cipher (well, you COULD solve it with one, but only if you have a few hours and are derailed)

If you’re reading this guide, you almost certainly don’t need this clarification but: everything that follows takes place in the Tech Nexus (Texas, ladies and gentlemen) in the Expedition DLC.

The Musical Notes File:

This is on the ADMINISTRATION floor, in a terminal on the south side. It’s in Mickey’s email. Take a screenshot or write down the notes (PLUS the spaces).

Note that sharps and flats come after a note, not before it, so

C#C is C# followed by C, NOT C followed by #C.

The Transposition Guide File

Not strictly necessary, but keeps you from googling. This file is also found in the ADMINISTRATION floor, in the same computer as the notes file. It is just a handy guide telling you how many notes to shift. We’ll explain what that means later!

The Key File:

This file is found on the SECURITY floor – you’ll know it because there’s a shooting range with a target in view of the elevator.

The file you’re looking for is in the southeast corner room – it’s another email chain. You’ll have to click around until you restore a certain file. It will have interval and octave keys. Make sure you get Mickey’s key! (In other words, that the name from the key file matches the name from the notes file)

Don’t worry if you don’t know what any of that means, that’s later in the guide!

Also screenshot this file. And that’s it!

The Basic Code

Ok. So our goal is to end up with a 4-digit number.

You’ll notice that the musical file has four lines. Each one of these lines contains a number – either an actual integer (1,2,3…) or a number spelled in English.

We need to translate the notes into English letters/numbers. Each note codes one letter / number.

So, how are they coded?

Well, let’s go through it as simply as possible. This is a musical cipher, so it uses musical notes.

Musical notes go in the following order:

Except that’s not quite all. Between some notes there are sharps/flats. Each one of these notes goes by two different names. The ‘#’ means sharp, and the ‘b’ means flat.

Each dotted box contains one note, with both it’s names. So C# and Db are the same note.

So one full set of notes is C, C#/Db, D, D#/Eb, E, F, F#/Gb, G, G#/Ab, A, A#/Bb, B.

One full set is called an octave.

In this cipher, there are three octaves, so the full set of notes there can be is:

Underrail - The Utter Pipeworker's Guide to the Musical Cipher

Each octave starts with a C, and ends with a B.

So: if there were no shifts, we could just decode all the notes in the following way:

Underrail - The Utter Pipeworker's Guide to the Musical Cipher

Shifts and Octaves

Of course, it couldn’t really be that simple, right? This is Underrail, and this is a code set up by a bored scientist! Of COURSE there are complications!

If you paid attention to the first mapping of letters and numbers, you saw there was a problem: how do we tell which of the three octaves the note belongs to?

The answer to THIS is found in your Key File!


As you’ve seen, there are four octave keys. Each of these (in order) matches with one of the lines of musical notes in the notes file

Notice that each of the octave keys starts with three numbers, and further notice that each octave key has three more numbers than there are notes in the corresponding entry in the notes file.

And FURTHER notice that each line starts with the SAME three numbers.

That’s because the first three numbers match to the three octaves. So, for instance, in my case, Mickey’s key file had “603” at the start of every line.

That means the leftmost octave is called octave 6, the middle is octave 0, and the right is octave 3.

So that means that the very leftmost note is A6, and that octave stretches right until B6. The next note is C0. Clear?

Why we couldn’t have just called the octave 1-2-3, I don’t know. The other players weren’t even supposed to get the key file! Oh well, scientists!


You’ll notice that there are three entries under “interval key” in the key file. Let’s call them A, B, and C.

Mine were “Major Third”, “Major Second”, “Major Sixth”

These are here because each of the notes has been shifted by some amount.

Notes in the first octave are shifted by the first entry in the interval key, we’re calling it “A”.

Notes in the second octave are shifted by “A” plus the second entry in the interval key, we’re calling it “B”

Notes in the third octave are shifted by “A” plus the third entry in the interval key, we’re calling it “C”

All shifts are to the left: If you have to shift A# by three, it goes A# -> A -> G# -> G. Always consider the sharps/flats as regular notes for shifts.

Let’s call the three octaves “X” “Y” and “Z”, and the three shifts “A”, “B”, and “C”. Then:

Underrail - The Utter Pipeworker's Guide to the Musical Cipher

Now, you may note that the octave key also contains “7” “1” and “4”.

When you see a number one greater than one of the octave numbers, this means that we start out ABOVE that octave, but when we apply the leftward shift, we’ll end up in the correct octave.

In other words, If our note was C in octave “7”, and we shifted by 1, we would end up with B in Octave 6.

Why not simply call it octave 0, which is the second octave in my case? Because we’re applying the shifts from octave 6 (“A”), NOT the shifts from octave 0 (“A” + “B”).

You’ll always end up in the octave whose shifts you are using!

*Grabs My Throat* How Do I Solve the Cipher.

OK OK OK! Eaaaaaasy. Easy does ‘er!

First, let’s assemble the keyfile and notes file.

Again, this is randomly generated so yours will be different.

Alright. So first look at the keyfile. The first three numbers in each line are 6-0-3, so the three octaves are called 6, 0, and 3.

We can see that the first octave is shifted by a major third, the second octave by a major second, and the third octave by a major sixth. That’s…

Shifted by 4 for the first octave (Octave “6”)

Shifted by 4+2 = 6 for the second octave (Octave “0”)

Shifted by 4+9 = 13 for the third octave (Octave “3”)

So let’s take a few letters of the first line:

Do notice that the first “603” in Key 1 isn’t part of the code – that’s the octave key!

So let’s do the first word: get out the notes guide!

Underrail - The Utter Pipeworker's Guide to the Musical Cipher

So Gb in octave “6” (first octave) means it’s shifted by 4. Gb four to the left is D, which is “C”.

G# in octave “0” (second octave) means it’s shifted by 6. G# six to the left is D, which is “O”

B in octave “0” (second octave) means it’s shifted by 6. B six to the left is F, which is “R”

E in octave “6” (first octave) means it’s shifted by 4. E six to the left is C, which is “A”

Eb is in octave “7”, which means it starts outside the first octave (6), but still uses octave 6’s shifts. That’s a shift of 4. Eb shifted by 4 is B, which is “L”.

First word: coral! Aqua-themed, appropriately music-y, we’re on the right track!

Go and do likewise, and reap those benefits, maniacs!

Volodymyr Azimoff
About Volodymyr Azimoff 13372 Articles
I love games and I live games. Video games are my passion, my hobby and my job. My experience with games started back in 1994 with the Metal Mutant game on ZX Spectrum computer. And since then, I’ve been playing on anything from consoles, to mobile devices. My first official job in the game industry started back in 2005, and I'm still doing what I love to do.

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