This paper presents the design and construction of a homemade sound tube demonstrator that doubles as a functional musical instrument. Developed as a pedagogical tool, the prototype aims to introduce children to fundamental musical concepts such as sound production, pitch, and scales. The design process involved validating the instrument’s operation as both an open and closed tube, with special attention given to determining the precise tube lengths required for accurate tuning. The study addresses theoretical challenges, such as material selection and tuning techniques, alongside practical considerations to ensure the prototype is both accessible and durable. Acoustic measurements were conducted to validate the theoretical predictions and ensure accurate tuning of the instrument. To assess its educational impact, the demonstrator was tested in a public educational setting, where children engaged with it through guided activities. The results show that the tool helps inspire musical curiosity and makes learning more engaging through hands-on activities. This work highlights the potential of simple, low-cost instruments as educational resources, contributing to both acoustic design and music. The sound tube demonstrator exemplifies how functional hyper-instruments can bridge science and art, inspiring future generations to explore music and acoustics.