WM-BF40

The WM-BF40 is a mid-tier FM/AM radio cassette Walkman that added low and high equalizer controls plus a Mega Bass switch to the standard radio-and-tape formula. It uses a compact plastic body with a metal-decorated cassette door, manual tape selector, and two-AA power system, allowing users to shape the sound more actively than on the simpler tuner models around it. The result was still portable and fairly compact, but with a more obviously audio-tuned identity.

Sony was layering branded sound features into the radio branch instead of reserving them for playback-only models. It was not a flagship, but it gave users a more involved listening experience without making the machine feel premium or complicated. It reads more as a very late-1980s Sony way of adding value.