Since I am a musician, I like my children to not just listen to music, but when possible, listen to the best music, and I like to expose them to classical music much of the time. There have been some wild claims made about music, but I'm convinced that music that is better quality has been great for my children's overall mental and emotional development. For lullabies, I would suggest you try this link - they are not only well produced, but have some classical pieces as lullabies too - the best of both worlds!
Baby Lullaby Music