Row, row, row your boat, gently down the stream……  How many times did you sing that as a child?  Over and over!  What about singing it in a round?  You eventually learned to distinguish the verses and could listen to them together or make them out separately.   That idea is very similar to the theory behind BabyPlus.  The two sounds, mother’s heartbeat sounds and BabyPlus, are simultaneous but the prenatal child eventually can discern that there are two different sounds.  Learning to distinguish is one of the most basic learning skills which is the foundation for baby’s development after birth.