Final answer:
Bottom-up processing is the best explanation for the phenomenon described in the question.
Step-by-step explanation:
The phenomenon described in the question is best explained by bottom-up processing. Bottom-up processing is a type of perceptual processing in which sensory information from the environment is used to form perceptions. In this case, the sad music influences the perception of the spoken word, causing it to be perceived as 'mourning' instead of 'morning'.