If you haven't already been playing music for your newborn, start immediately. Soft instrumental music is great beginning music for newborns as the soothing repeated melody is a similar to his days in the womb.
Vary this activity by changing the music selection to a more upbeat instrumental melody and see if your baby reacts any differently - look for changes in his eyes as well as his face and movement of his hands and feet.
Begin to choose a variety of musical selections and continue to watch the reactions of your baby. . . to this day my son's preference is still the country music his father usually had playing in the house and car.