This paper presents the SIBILIM, a low-cost musical interface composed of a resonance box made of cardboard containing customised push buttons that interact with a smartphone through its video camera. Each button can be mapped to a set of MIDI notes or control parameters. The sound is generated through synthesis or sample playback and can be amplified with the help of a transducer, which excites the resonance box. An essential contribution of this interface is the possibility of reconfiguration of the buttons layout without the need to hard rewire the system since it uses only the smartphone built-in camera. This features allow for quick instrument customisation for different use cases, such as low cost projects for schools or instrument building workshops. Our case study used the Sibilim for music education, where it was designed to develop the conscious of music perception and to stimulate creativity through exercises of short tonal musical compositions. We conducted a study with a group of twelve participants in an experimental workshop to verify its validity.