No, it did not install a virus on your iPad. And you cannot download music files from a website using Safari (it doesn't have that capability). You might the app store or the site to see if a specific app is recommended.
As for being legal, I'm not familiar with the site. You might try a Google search.
The only way to put your device in danger of getting or spreading a virus would be using modified software:
Transferring media files is done through iTunes. Downloading music that you do not own is illegal.