This article defines the semantics of maquettes in the visual programming language OpenMusic (OM) using monads. A maquette can be seen as a sequencer of functions. Although maquettes have been widely used, their semantic have never been formalized. Formalizing maquettes has multiple benefits; primarily, we aim to provide a better understanding for composers through the use of a mathematical language rather than discursive semantics. In this work, we use a particular case of the state monad and show with examples how this monad is visualized in OpenMusic. The use of these advanced concepts in the field of music and their availability to composers aligns with our intention to bridge the gap between the theoretical and practical aspects of the intersection between mathematics and music.