Download products - add to cart from the category page?

I am building music library. My products are music files, which are consider to be virtual products or downloadable. I know how to set it up with options attributes ect. My page has several categories: classical, new age, pop, rock etc...
Once you open category page you will see few demo songs. You can click the play button and flash player will play it on the same page. Right to the demo song there is a button "buy now" . How do I set up that button to the product? If I do it with option attributes the "...more info" shows up and directs me to the next page, which I want to avoid.
You can check the incorrect set up at:
http://www.enetimusic.com/index.php?main_page=index&cPath=1_4

Please help. Any suggestions?

If your products have only one attribute each, then you could use this: http://www.zen-cart.com/forum/showthread.php?p=809142#post809142
Remember, that post was based on v1.3.8, so if you're using v1.3.9 or newer you'll need to adjust the code accordingly.