Sonic, Sound, one of those. It's by Sonic Foundry. I got my copy with my Sound Blaster, but it can be bought I think at software outlets. There are two versions, a $50 and $300 version for pros. I think Acid is around $200 or $300. I'm sure there are all kinds of products that will add sound to an animation. It all depends on what you need vs what you will spend. For adding sounds and music, I like SOUND FORGE.