An instrument played by hitting a series of rocks has been created by designers at Italian research group Fabrica for a member of their music team's latest album (+ movie).

Fabrica designers Ryu Yamamoto and Leonardo Amico mounted stones on wooden pillars to make musical keys that play notes when they are pressed, creating a musical instrument digital interface (MIDI) controller similar to those used by many electronic artists.

The Stone Pad instrument was played on tracks from the latest album by Jhon William Castaño Montoya, a Colombian violinist and researcher in Fabrica's music team.

"The idea was to make a musical instrument that would reflect Jhon William's music spirit," Yamamoto told Dezeen.

The design is based on a scale used to classify minerals devised by German scientist Friedrich Mohs in 1812. The Mohs scale ranks minerals in order of their ability to scratch others - with diamond being the hardest and talc the softest.

Castaño Montoya named his album after the scale, so the designers chose to extend the idea to an instrument with rocks for keys.

"John was considering this as a metaphor of growth: a progression of experiences that affect you but makes you stronger," Yamamoto said. "This element of growth has a big influence in the design of the object: the wooden stems blossoming from the base of the instrument and the stones positioned in rising heights corresponding to ascending sounds."

Instead of trying to represent different materials, the designers used rounded stones as the keys so they could be played easily.

"Apart from aesthetic choices we were also constrained by the fact of the object being playable, and this kind of rounded stones were the most suitable for that goal, without needing to modify their shape," Yamamoto said.

Pressing the stones sends signals along electrical wires to a computer that converts the pulses into sounds. Low stones correspond to low notes, ascending to higher notes as the pillars spiral upward.

"The rising spiral shape is an exotic musical interface, but it still retains a fairly clear visual reference for musicians to play it," said Yamamoto.

Photography is by Marco Zanin of Fabrica.