The pitch-based input (humming, whistling, singing) in acoustic modality has already been studied in several projects. There is also a formal description of the pitch-based input which can be used by designers to define user control of an application. However, as we discuss in this paper, the formal description can contain semantic errors. The aim of this paper is to validate the formal description with designers. We present a tool that is capable of visualizing vocal commands and detecting semantic errors automatically. We have conducted a user study that brings preliminary results on comprehension of the formal description by designers and ability to identify and remove syntactic errors.