MM-RT (material and magnet - rhythm and timbre) is a tabletop musical instrument equipped with electromagnetic actuators to offer a new paradigm of musical expression and exploration. After expanding on prior work with electromagnetic instrument actuation and tabletop musical interfaces, the paper explains why and how MM-RT, through its physicality and ergonomics, has been designed specifically for musical wonderers: people who want to know more about music in installation, concert, and everyday contexts. Those wonderers aspire to interpret and explore music rather than focussing on a technically correct realization of music. Informed by this vision, we then describe the design and technical implementation of this tabletop musical instrument. The paper concludes with discussions about future works and how to trigger musical wonderers' sonic curiosity to encounter, explore, invent, and organize sounds for music creation using a musical instrument like MM-RT.