Correct answer: “It depends!”
Music needs to be personalized for the individual you are caring for. Play the wrong music, increase the pain… play music that resonates with the person, you may be able to help decrease the pain.
Peaceful music, combined with beautiful photography may decrease stress for those who can relax to the music. As I watch this video (Prelude in b flat minor, J.S. Bach) from Room 217 and enjoy the images I feel peaceful. When my grandson, then 4 years old saw this for the first time, he was mesmerized and focused on the music and the images. For both of us, I think the music video would have decreased pain.
In a previous blog I mentioned about using music to stimulate 
learning. I provided examples from Broadway Musicals. These particular songs could increase tension and increase pain if the person did not like the style of music, the message in the lyrics, or a memory attached to the music.
A principle of hospice palliative care is to individualize care. With any comfort measure I suggest “Respect the individual and individualize the care”. This holds true for music as well as for any other care.
