Loading the music
The problem I faced when first loading in the audio is that it too for ever, and because of the way that the audio system was designed I couldn't split up the loading times, or else the loading screens between the levels would last just too long and get yuuuuusssttt annoying enough. (Note that this is device dependent, some smartphones will be faster than others)
That's why I chose to load in all the music at the start and add a "Restart Game" Button.
The reason why there is a restart game button to, basically, reload the entire game EXCEPT for the audio, which only gets loaded right after the game is first launched. That is because the "Restart Game button only loads the scene right after (scn_StartUp_03), which also destroys all the objects in the "DontDestroyOnLoad" scene Except for, again, the AudioController object that contains the music. That way it doesn't have to reload all the songs! WOO!