*In process of stocking* Spaniard Francisco López is one of the most recognised sound artists on the international scene: in the span of four decades of activity, he has developed an extremely personal sound universe, based on a deep listening of the world. He created hundreds of sound installations and performances in major museums, galleries and international festivals.

Reinier Van Houdt, Dutch pianist and composer, has built himself an unusual repertoire that is always the result from personal quests, from collaborations with musicians to researches in archives; at AngelicA he played as a member of MAZE, in duo with Michael Pisaro, as soloist with the Orchestra del Teatro Comunale di Bologna for Yannis Kyriakides, and in solo for Walter Marchetti's Concerto for the left hand; he is also part of Current 93, and has collaborated with Alvin Curran, Christian Marclay and Jürg Frey among others.

untitled #400 is a project presented as a world premiere by Lopez and van Houdt at the opening of the 31st edition of AngelicA, on 15th May 2021. The two musicians already worked together on untitled #275, a performance for mechanically prepared piano, quadraphonics and electronics which received a special mention at the 2011 edition of the Ars Electronica festival in Linz. In comparison to the piano “preparation” implemented in #275, the concept behind untitled #400, developed during six years, effectively introduced a new instrument: a “stringless piano” (or “inside-out piano”), whose initial inspiration came from Lopez’s installation The [Music] Room presented at the Caramoor Centre for Music and Arts in Katonah (New York), in which a Disklavier piano in full automatic performance could be seen playing, but without hearing the notes associated to the keys, since the hammers were not touching the strings.