The MCA-Matsushita deal offers a bright hope for change at Yosemite, which is under relentless siege by tourists, traffic and commercialization. The Yosemite Valley concessions will now go to a new contractor, who can and should be held to a "less is more" philosophy - that fewer parking spaces, hotel rooms and shops will make the park a better place.

A condition of the MCA purchase is that Japan's Matsushita must sell the Yosemite Park and Curry Co., which runs the park's concessions, to an American buyer within a year.Yosemite, with 3.4 million visitors annually, has been ill-served by its current concessionaire. The Curry Co. pays less than 1 percent of its revenues for exclusive concession rights. Indeed, conservationists concerned about smog, overcrowding and other park troubles have already joined as part of the Yosemite Restoration Trust to challenge the Curry Co.'s 30-year contract, due to expire in 1993. The trust aims to put into effect the 1980 management plan that calls for reducing hotel facilities and private cars in Yosemite.

The National Park Service, with backing from Congress, must now assert itself and make sure the new concessionaire not only pays more but is serious about reducing the congestion at Yosemite. The new contractor must have a strong commitment to preserving Yosemite and be held strictly accountable for doing that.