The fetus reacts with movements to both music and unstructured noise. Auditory perception may be earliest trigger for fetal recognition of an outside world. (Storr, Anthony. Music and the Mind. p 8-10. NY: Ballantine Books, 1992.)
Enrichment Program: Select a few musical pieces and play to the fetus, and they may calm the baby after birth (e.g., Air on a G String by J.S. Bach. Other examples include slow steady selections by Haydn, Mozart, Beethoven, Vivaldi). (Diamond, Marian, PhD, and Janet Hopson. Magic Trees of the Mind. p 97-99. NY: Dutton, 1998.)
Refer to Brain Development, Fetal for additional information.