The “Concerto for the left hand in one movement”, for piano, is the last unpublished composition of Walter Marchetti to be performed in public before the death of the author on May 12, 2015. Composed in 1994, the “Concerto for the left hand” belongs to an ongoing series of works written between 1994 and 1997: “Con vista sui suoni”, “Eight or Nine Movements for String Quartet” and “La perdita del tempo” which develop from a preceding composition titled “Canonic Variations for Orchestra on Prolapsed Time From Development to Hiccup of Black Cherry Jam”. In these works Marchetti made a systematic and assertive return to conventional music notation, even while not excluding performative and installative practice and the use of pre-recorded “concrète” sounds which from the 60s had been his privileged field-of-action. A modality shared principally within the exquisitely iconoclast and desacratory activities of the ZAJ group. What was particularly interesting to Marchetti in this recourse to musical writing is weakening the meaning of the rigid normative apparatus of a musical score with the purpose of annihilating the factual potential of his system of prescriptions. The title alone is used to hide a paradox where the notes to the performer intervene to subvert the following paradigm: “The pianist is obliged to hold a black umbrella opened over his head in his left hand during the whole performance of this concerto”. From here the performer is confronted with two conceptually convergent possibilities in de-potentializing the apparatus of signs in the score: the restrictive imposition of the paradox where the music couldn’t manifest itself in case of respecting to the letter the enunciation which lead to the impossibility of the music’s ‘existence’ (i.e., the obligation of holding an open black umbrella in the same hand) or rather, transgressing this encumbrance, the implicit possibility of playing the score with the right hand and, definitively, the condition of the music subjected to its own manifestation to no longer be able to coincide with its own realization: “a magic made free from the lie of being truth”.