Can't live without . . .

oxygen, water, shelter, food. My initial thought was music but that is rather a cultural luxury. Printed music scores are lifeless until one takes a breath to sing . . .

EDIT: Cultural luxury? Music seems natural to human beings. We each have an instrument to use but so many seem reluctant to use it. What if only the best songbirds sang? The forest and meadow would be a quiet place indeed. My fondest memory of my last visit to England was waking to the dawn chorus.