Update: SB Composer has updated! Download here http://starboundcomposer.com/
I'll leave this up just in case for whatever reason you need it.

Hello, and welcome to this guide. If you didn't see already this is only for if your Starbound Composer shows "None" as an instrument, and nothing else. It isn't very hard to fix too, and (besides downloading Starbound Composer & Starbound itself) you don't need any additional programs to do this. Also, this is Windows only. It may work with other operating systems, but I don't know.

• 1. Navigate to your Starbound Installation folder
  
  
• 2. Left click the "win32" folder once (to select it, even if you are 64-bit), hold down the SHIFT key on your keyboard, and then right click it.
  
  
  
  
• 3. In the context menu, click "Open command window here"
  
  
  
• 4. In the command prompt, type in "asset_unpacker.exe" letter for letter. Next, in double-quotes, type in the location of the "packed.pak" inside \Starbound\assets\ (Your location is more than likely not the same as mine) Then push space, and type in a location in a new folder of your choice in destination (just make sure you remember where it is)
  Example:
  
  
  
• 5. Double check for typos, and then push enter. If everything goes well it will start unpacking the game files where you specified.
  This may take a while.

You can do this while you are waiting for the files to extract.

• Navigate to your Starbound folder, then to "mods"
  
  
• Create a new folder called "defaultinstruments", and open it
  
  
• This section containing info on the .modinfo was removed, I found out by accident it isn't needed
  
  
• Create two new folders. One named, "items", and the other named "sfx"
  
  
  
• Now you have to wait for the files from earlier to finish extracting. If they are, then go to the folder you specified. First, look for "items". Open it, and copy the "instruments" folder, then paste it into the items folder from your mod. Do the same with sfx, copy the instruments folder from \extracted stuff\sfx\instruments and paste it in your mod sfx folder.
  

You should be finished now, if everything went right.

Open Starbound Composer and check if the instruments are there. Make sure in the preferences, that it looks for mods.

If in the end you didn't get the instruments, please comment and I will try to help you. Also, if you spot any mistakes, comment for that as well and I'll try to fix it up. If enough people have trouble with one area I may add screenshots or explain that area further.

If you have issues, first make sure your mod directory matches this (this image doesn't show files, just folders)


Well, hopefully it works for you. Enjoy!