Children whose brains don't make those connections at an early age may never make them. That's because after a few years their brains stop making so many connections and start pruning unused neurons. That's not to say children won't benefit from music instruction later in life. One study even found that college students improved their reasoning after listening to a Mozart sonata, but the effect lasted only 10 minutes. Nor does the study suggest that music is the only way to make those connections.
Children learn in many ways.
But there aren't very many ways to do such serious learning while having so much fun. At a minimum, Rauscher's findings make a strong case for integrating music into learning as early in life as possible.