The sounds from the special metal plates of the Primary series are sized 35 x 5 mm (Soprano/Tenor Alto) or 35 x 10 mm (Large Bass). Each sound plate is printed with the image of the corresponding note, facilitating the process of learning music through visual reference.

The resonances of the Sonor Primary Metallophones are fully certified by FSC®. In addition, an eco-friendly varnishing system called Proterra is used, which is based on shellac, oil, and carnauba wax.