One day playing on my server, using the latest version at that time, I was listening to the music. I heard the C418 music playing. Then a new song was playing simultaneously with the other one. It also does it with the secret song update.
I thought that it should play one song at a time.
But it played two (or more...) songs at once.
To get this to work use these steps:
1. Go into creative mode (found out on a server)
2. Listen to the music
3. Wait until the game makes two songs.
Related issues
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53rd Duplicate of MC-35856 - If you have not , please use the search function in the future, to see if your bug has already been submitted. If you could not find the original report, please comment with the keywords you searched for.