Campbell Music Co., suffering from a recent sales decline and a shortage of cash to pay bills, has sought court protection under Chapter XI of the federal bankruptcy laws.

The music merchandise retailer, celebrating its 40th birthday this year, plans to continue operations at five Campbell retail outlets in metropolitan Washington and one store in Harrisonburg Va., that operates under the name Hayden Music Co., while seeking to reorganize debts voluntarily with creditors under the bankruptcy code.

A filing at federal bankruptcy court in Alexandria for Keyboard of America Inc., which trades here as Campbell Music, does not list assets or liabilities. A more detailed statement will be filed in court June 10, the court documents state.

Jim Hayden, president of Keyboards/Campbell's, did not return a reporter's telephone call yesterday. Apparently, after a depressed period in the late 1970s when Campbell's share of the local market declined, sales by the retailer have increased sharply over the past two years, to about $3 million a year, and ongoing operations have been profitable.

But the costs of opening a store in Laurel and debts from earlier entities became a problem when sales declined in April, and one creditor reportedly sought the return of its merchandise from Campbell's inventory. Long a leading seller of pianos, organs and other music goods, Campbell's has stores downtown, at Tysons Corner, Springfield Mall and Wheaton in addition to Laurel and Harrisonburg, and an Arlington warehouse.

The company was founded here in 1941 by Earl Campbell, who had been in charge of Hammond Organ Co.'s New York store when armed forces chaplains needed 550 organs and Campbell decided Washington would be a good location for a music store he had wanted to own.

Campbell sold the retail chain in 1968 to a group of Washington investors and ownership of Campbell's has changed hands several times since, with successive owners unable to build sales volume and profitability in the wake of changes in music taste and new retail competition.