Can lambda calculus be transformed to an artistic expression and if so, what could it sound like? This paper discusses the CodeKlavier’s Ckalcuλator: an arithmetic calculator for the piano following lambda calculus principles. The Ckalcuλator is the fourth sub-system of the CodeKlavier project whose goal is to become a performative programming language with the piano as interface. Lambda calculus, as a well understood formalisation of computation, can be an important foundation to any system desiring to become a computer language and the Ckalcuλator is the result of this formalisation in the CodeKlavier’s development journey. Performing lambda calculus with the piano adds a conceptual, creative and performative dimension to otherwise simple arithmetic operations. This paper gives a brief introduction to the project, discusses the motivation, the system, and its artistic application before reflecting on the project’s future.