the.com/thumb piano

means A small African instrument made of metal tines fixed to a wooden board or box, plucked with the thumbs (and sometimes forefingers) to produce soft, bell-like tones.

from The instrument itself is ancient and African, with roots going back well over a thousand years and countless regional versions — mbira, kalimba, likembe — each with its own tuning and spiritual role, especially in Shona culture in Zimbabwe, where the mbira is central to ceremony. 'Thumb piano' is simply the descriptive English nickname outsiders gave it: no relation to the piano's hammers and strings, just a borrowed name for the keyboard-like row of metal keys and the thumbs that work them.