Pain of any sort, whether muscular, skeletal or other cause is not pleasant and can affect the quality of our life. At night it can disrupt our sleep patterns leading to an increase in stress levels which in turn can intensify the pain.
Have you ever cut yourself accidentally but didn't realise you had done this for some time? Incredibly even though you were cut a pain signal did not arrive at your mind. Only a while later when you realised you were cut did you become aware of a throbbing sensation or even some pain.
If the mind can ignore a cut it can also reduce any existing pain you might have no matter what the cause. Why even in India in the 1800's a British doctor operated on patients who had been taught self hypnosis and they felt no pain.
Even if this self hypnosis mp3 just relieves some of the pain it has to be worthwhile. It may of course do even more than that. Don't forget that pain is a signal to the mind that something is wrong in the body and should not be ignored. Report any pain to your doctor before using anything else.