There is more to the aesthetic experience than form. Even though forms might be present, the forms themselves might not be fundamentally significant to the cognitive/empathetic/emotional/etc experience afforded by the work of art.
David Byrne’s Playing the Building of course requires the physicality of the building in order to produce the desired sounds, and of course this physicality presence a specific set of aesthetic values-a specific form-however I hesitate to understand the experience afforded by the piece as a whole to being merely a formal one. I can imagine young students researching the piece in order to further inquiries into the nature of sound; music students might be able to create entire dissertations about the musicality of place and the search for musical scales in abandoned buildings.
notas desde el inxilio 
Absolutely a limitation to try to pigeon hole art and our experiences and understandings of it.