Some sources say it has quite an effect.
In fact, so much of an effect as to make former Georgia Governor Zell Miller give a free compact disc or cassette tape of classical music to the parents of all babies born in his state's 100 hospitals in 1998. Miller, an avowed country-music lover, is convinced that music can stimulate brain development in young children. And having an infant listen to soothing music helps trillions of brain connections to develop. In this study, they used the same task as in their first experiment but extended the types of listening experienced. Only the Mozart group showed a significant increased spatial IQ score.