This short film gives a front-row seat to the premiere of Roberto Gerhard's musical "divertimento" Claustrophilia (1966), for eight harps, four wireless receivers and two monitors. Claustrophilia was purposely conceived by Gerhard in response to John Cage's request for a manuscript page for his famous catalogue "Notations". Accompanying this page—sent to Cage as a "Christmas postcard" in December 1966—, Gerhard expressed his wish for John Cage and David Tudor to conduct its performance. This film picks up for the first time Gerhard's challenge in the year of John Cage's 100 anniversary.