Turn the beads, thread the rods, set the frame. The Banshū abacus workshops in Ono keep three separate hand operations running: turning the beads, fitting the bamboo rods, and assembling the frame around them, each done by different people. Some will let you try the assembly, and doing so reveals how narrow the tolerance between bead hole and rod actually has to be for the thing to work at all. Too loose and the bead drops of its own accord; too tight and it will not travel when you want it to. The sound an abacus makes when you sweep it with a finger comes directly out of that clearance, which means the sound is a design decision rather than a by-product of one.

Nobody set out to make an instrument, and yet the tolerance was chosen partly by ear. Sannomiya is about an hour away by rail and road, the town has its shops and hospital, and housing is inexpensive by the standards of the prefecture. Nobody has arranged anything here for visitors and the workshops are working premises.

As a calculating instrument the abacus has largely finished its working life, and everyone involved in making them knows this perfectly well. The beads are usually birch or boxwood and the rods are bamboo, chosen because bamboo is straight, light and does not swell in humidity. Production peaked decades ago and has fallen a long way since, which the workshops discuss without much drama. What continues is largely for schools and for competitions. It has gone on being made anyway, partly for schools and partly for the sound, which is a strange and rather good reason for a trade to keep going into a century that has no use for it.