Cavern is a collaboration between Australian artists Sleep D and Ad Lib Collective. Sleep D is an underground electronic music duo and Butter Session label heads. Ad Lib Collective is a classical mixed chamber ensemble.

Cavern is the first record release from Play On, a Melbourne based classical/electronic music events company and now record label. Sleep D x Ad Lib Collective's recorded work is a culmination from a two-year project borne out of a live performance at Play On show in a Melbourne underground carpark. Limited to 150 physical copies, this single is taken from the upcoming full length album Flashed Glass.