I only looked up Mutagen Puzzle explanation, but not solution (It's way better explained on the wiki). It's actually rather easy once you understand it, although you do need an online notepad open to save the mutagen codes. It works like a Tetris/Candy Crush/Abacus, you add mutagen in a specific order to get a proper chain.
Dude's puzzle is the easiest. There are three papers with codes hidden in the same room. The console gives a list of scrambled text, in it there are (only) three numbers spread across, two on the sides, one in the middle, you combine them and see which of the three papers the combined number fits. Repeat until done.
The Musical Puzzle in DLC I've yet to try at all. Same for Emergency Phones, which is an actual music puzzle, and it gives me PTSD of Myst.
*edit* Done two of the Emergency Phone music puzzles on Easy to test it out. Not as bad as Myst, since you can start a "demo" playback AND test out all the sounds at the same time if you are quick enough. Again using an online notepad to write down the correct sequence, which you can then replay manually. Only two of the six sounds are very similar: yellow and blue. All in all it's tedious, but doable.