The Sony unit is cheaper.

The home base station of the Sony unit is smaller.

When connected to five speakers, the Sony unit can also create sound environments, though they do not seem as subtly detailed as Yamaha's.

I tried a Sony unit; models with virtually identical functions but different designs are available with Mitsubishi and Philips Magnavox labels.

According to officials of both companies, the agreement enables the Sony unit to create interactive programming for Interactive in conjunction with its own television programming and third-party programmers.

"At first there was a glitch in programming with the Sony unit," he said.

"Electronic distribution is looming," said David H. Kawakami, director of sound technology marketing for the Sony Software Corporation, a Sony unit.

Mr. Olaffson and Mike Vitelli, president of personal audio products, the Sony unit handling the hardware, denied reports of internal strife.

He used that position, as well as long experience at Sony, to pull in engineering talent and technology from 20 different Sony units.

It's best not to go too cheap here, and at only $22 for a Sony unit, it's hard to believe you can get much cheaper.