Utilize the input text as a context reference, choose the right relationship between Walkman and Sony from the options. Options: product/material produced, manufacturer, distributed by, industry, position held, original broadcaster, owned by, founded by, distribution format, headquarters location, stock exchange, currency, parent organization, chief executive officer, director/manager, owner of, operator, member of, employer, chairperson, platform, subsidiary, legal form, publisher, developer, brand, business division, location of formation, creator.

The reason Sony unveiled not one, but two different digital Walkman devices in 1999 was that it was hamstrung by silos: different departments of the giant Sony empire had each developed its own, different digital music devices.

Answer: manufacturer