TOKYO -- A musical revolution in Jamaica has a connection with a bouncy rhythm from a portable electronic keyboard that’s the brainchild of a Japanese woman.The pattern that resonates in the 1985 reggae hit by Wayne Smith, “Under Mi Sleng Teng," came from Casiotone MT-40, which went on sale in 1981, the first product Hiroko Okuda worked on after joining the Tokyo-based company behind G-Shock watches.“It’s really like my first child, and the child turned out so well it’s outright moving,” said Okuda, honored as “the mother of Sleng Teng” among the hard-core reggae aficionados.Sleng Teng is a form of digital Jamaican music that began in the mid-1980s, part of the rich repertoire of the disco-like genre called “dancehall.” No one contests the key role played by artists like Smith and King Jammy, as well as the humble, battery-operated, $150 MT-40.One of the rhythm patterns Okuda created called “rock” on the MT-40 evolved into “Sleng Teng riddim.”As legend goes, Noel Davey, the Grammy-winning keyboard player for the Marley Brothers, got an MT-40 from a friend, who picked it up in California.