Is the prayer of one who completes it valid, after having entered into it fearing that there might be something invalidating it, and then it becomes clear to him that what he feared does not invalidate the prayer?

We advise you to turn away from whisperings (waswas) and not to pay attention to them, for the default is the validity of prayer and ablution. They are not invalidated except by attaining certainty of what invalidates them. So, prayer in a place where there is music is not invalid, nor is it invalidated merely by the fear of the existence of something that invalidates it. Rather, there must be certainty of the occurrence of something that invalidates the prayer or ablution.