Its all in the course, anyway
None of the 3 are mandatory for the course, but highly raccomended
Meditation guide your brain between theta and delta brainwaves. This increase your ability to receive energetic informations from any other audio you listen to afterwards.
I suggest using it also outside of the course when you meditate, and if you dont usually meditate… I suggest start doing that 
Ego dissolution lessen for sometime the grip of the ego, your illusory separate self.
On a physical level promotes neuroplasticity, so again it will increase your ability to receive energetic informations from any other audio you listen to afterwards.
Again it is also very good on its own, for example when you are meditating…and if you dont usually meditate… I suggest start doing that 
Emotional release is there because during the course, and I say with any good spiritual path there is a strong component of healing on all levels. This can bring up strong emotions that may be difficult to be accepted and then released if one isnt quite used to do that.
If you feel sadness, fear, anger… during the course, this audio does all of the above for you.
Emotions are held in multiple layers, so again this audio can be very useful on its own… for example when meditating… and if you dont usually meditate… 