Question

Artworks made using alternative media are best accessed by but often exist only in the form of

Answer 1

Artworks made using alternative media are best accessed by direct experience but often exist only in the form of visual documentation or personal accounts.
Alternative media is popular with a certain niche of people - it is obviously not mainstream, so not a lot of people outside that particular niche know about it. It cannot be accessed in the 'normal' way, but rather only using various alternative methods.