Manufacturers of prenatal music belts claim that listening to soothing songs prenatally will help babies sleep well if they listen to the same music, once they are on the outside of the uterus. I have to admit that hearing songs I played a lot during pregnancy sent my babies straight to sleep and obviously, a prenatal music belt gets the sounds across much better! There are plenty of reasons to use something like a prenatal music belt while you are pregnant your baby will respond to sounds in different ways depending on whether they find the tune pleasant or not, and it might be seen as a great opportunity to bond with your baby before he or she is born. You will fetal movement in response to the music. And many people believe that listening to classical music stimulates the baby's intellect even in utero.
Apparently, these kinds of belts are totally safe. Would you use one? Personally, I think that it is a pretty clever business idea and that there are probably plenty of people who will buy it. But on the other hand, I am not sure that babies were really meant to be exposed to these kinds of loud sounds during pregnancy, and I think that hearing music on the radio or parents' voices is quite enough.