if i buy your player or mods,can i upgrade it for free?
do you have mod for audio, like guitartube.com?

Upgrade rules are enough explained on order page.
It is not free and is available only as our service.
New Player version is like completely new software, it is also like new, completely different installation, and in case of upgrade it requires even much more efforts than clean installation.

There is no audio mod or whatever you call it on Guitar-Tube site.
Guitar-Tube is not a member of Nuevolab Team. We work on different websites, but this doesn't mean so we can share such website's ideas or custom code.
It's certain company or website owners property and I don't think anyone wish to share own unique ideas, no matter who worked on it.