Add shopping Cart to phpsound script

I am looking for experienced programmer who can add shopping cart option to an already existing script called phpsound. I sell music online and I need to have shopping cart option "add to shopping cart" button on every track I sell. This script already has "buy now" field where you place paypal button link but that does not work for me. Also I need to have option if you buy 10 songs you get one free, 20 songs you get 3 songs for free.

Pricing Option muse meet the following:

Set price for all track with the option to manually enter and override that for individual song (this is for longer mixed songs I sell)

Two mp3 files will be uploaded for each track, one is 45 seconds long demo song and the other file is original full song.

Once the user successfully goes thru checkout procedure using PayPal, he will get the download links in his email or it will be displayed on the screen to download the purchased songs.

The website is currently live and in testing mode, please contact me for the additional information or just google phpsound on codecanyon to see the script

I forgot to mention that in current mode, I can drag and drop multiple demo songs at once and it will upload it without any problems to my server, since I have over 10000 songs this feature is the key to the whole operation. The demo (0:45 seconds) songs are the ones displayed and available to play. The original full songs (which are named exactly as the demo song) will be pulled from the separate protected folder after successful checkout with Paypal so it could be downloaded.

The whole point is, I don't want someone stealing original songs using different plugins or proxy tools.
And the process for me needs to be drag and drop easy for multiple files.
If someone has better idea how to do this, I am more than welcome to hear about it.

PHP Shopping Carts Software Architecture

Project ID: #10497452

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