Healing Sounds Question

​I wonder about the healing sounds pillar. Can each sound be used individually to bolster the energy of a specific organ system or do they need to be done always in a certain sequence like the 5 clouds meditation? 

For example, if one is having some emotion like worry could they just focus on the earth sound and color alone, or do they need to do the whole group in series? For those who struggle with grief, could they just use the metal sound and focus on clearing out the lung? 

Also, is the internal sound as effective as making an audible sound? 

What is the difference between the effect achieved by using an audible sound versus an internal sound? 

Can the internal sound effectively be used to move excess emotion out of the body?