Music or ambient sounds for meditation?

My own experience with meditation is that it works best when I'm alone and it's quiet. But in the dharma center they sell lot of cd's and many of them are titled "for meditation". Is it absolutely and definitely not "Comme il faut" to meditate with music? Is this music they sell for meditation more for rituals etc? Or is there some kinds of music that can be used for meditation? By "music" I don't necessarily mean melodic compositions, but ambient sounds like fex theta waves. Any experiences and/or advice?