I would stay away from the link you posted. There really isn't any credible information on that site and it sounds like a bad investment honestly. If you want to write better songs, simply study the songs you love and work to emulate that in your own writing. If you have something recorded already, please send it to me via e-mail and I would be happy to listen to it and give you some advice. I am a professional guitarist/producer/songwriter/composer living in Los Angeles and would love to help you in any way I can as a GT subscriber.