Expanding your Guitar Hero library on Xbox 360 requires navigating a landscape of delisted content and discontinued services. Here's the safe, legal approach.
On a modded/JTAG/RGH Xbox 360, tools like GH3+ Custom Songs or Phase Shift (PC) enable community-made charts. This requires hardware modification and carries Xbox Live ban risk.
Stick to official discs and previously purchased DLC for a safe, ban-free experience.