I was a strange child. I was probably the only 12 yr old going to the library and leaving with books about ballet terminology, Jane Austen and a pile of classical CDs. I enjoyed other kinds of music, but always have had a love of classical music.
That being said, I like to use classical music during playtime AND sleeptime and there are some really great CDs out there for both.
We've been using this for nap and bedtime. There are several other titles in this series which I intend on purchasing because I like this one so much.
I LOVE this CD. My kids can get REALLY wild when they play and this somehow helps with the CRAZY wildness. Still lots of play, minus a lot of crazy. This also helps my kids during craft time. They usually cannot sit with a craft for longer than 5 minutes, but craft times have now extended to 30 minutes. It's not an exact science...but it works! It's also lovely to listen to during cleaning :) Again, I am buying more in this series.
If you are familiar with the DVDs you will understand the "sound" of these CDs. It has a "baby" sort of sound and the kids sleep SOOOO well to these CDs.
This isn't classical but I've had this one for quite some time and it's such a beautiful CD. I mean who wouldn't want Jewel to sing them to sleep!
Again, not classical, but this CD will absolutely bless your socks off. I recommend any music put out by IHOP and Forerunner Music and this is just for children. Not just singing fun songs, but really worshiping and praying before the Lord, it's GOOD stuff. They have such an incredible vision for what children can do in the place of prayer and it is not done everywhere so this is worth a listen.
I found most of these at my local library in the children's section, which is a great place to try something out before you buy ;) I can't guarantee your child will be smarter or sleep longer, but there is lots of evidence to support the positive effects of music, so it's worth a shot :)