Bemoaning a ''lack of product,'' and with six of its nine usable Broadway houses either dark or not presenting theatrical attractions, the Nederlander organization, the second largest theater owner on Broadway, is preparing a series of concerts to fill its huge 1,933-seat Gershwin Theater in the fall.
So far, the organization has definitely booked one musical and one play for its other theaters - ''The Grand,'' a musical version of ''Grand Hotel'' directed by Tommy Tune, and ''Orpheus Descending,'' with Vanessa Redgrave re-creating her critically praised London performance in the Tennessee Williams play. James M. Nederlander, the organization's chairman, and Arthur Rubin, its general manager, say that although negotiations are going on for other shows, nothing else is definite.
''We're working on it,'' Mr. Rubin said. But none of those productions are for the Gershwin, the largest theater on Broadway, so the concert plans are going forward. Mr. Rubin said that the concerts would be similar to the Barry Manilow show now at the Gershwin, that Donna Summer was definite and that other possible performers included Gladys Knight, Gregory Hines, the Four Tops, the New Kids on the Block and Patti LaBelle. 'Our Basic Business'
Mr. Nederlander and Mr. Rubin maintained that the concert plans did not indicate they were curtailing their theatrical presence. ''We're in the legitimate theater business,'' Mr. Rubin said. ''That's our basic business. There's nothing wrong with doing a season of concerts.''
But their plan is the latest indication of the problems the Nederlander organization has recently had in filling its theaters. The last couple of years have not been the organization's best. It has had hits in ''Me and My Girl,'' the long-running musical at the Marquis Theater, and in Jackie Mason's one-man show, now closed, at the Brooks Atkinson. The jazz-and-blues revue ''Black and Blue'' is doing 70 to 75 percent of capacity at the Minskoff, and a couple of victories in next month's Tony Awards could help make that show a hit.
On the other side of the ledger, the Nederlander organization lost more than $5 million this season on ''Legs Diamond,'' which played at the Mark Hellinger Theater. Before ''Legs'' closed in February, Mr. Nederlander, saying there were no new musicals around, rented the Hellinger for five years, at more than $1 million a year, to the Times Square Church, which had leased the smaller and difficult-to-rent Nederlander Theater on West 41st Street. The church moved into the Hellinger right after ''Legs'' closed. The State of Broadway
To many theater people, the leasing of the Hellinger, which was the original Broadway home of ''My Fair Lady'' and which has long been considered one of the best and most beautiful theaters for musicals, was a sad symbol of both the state of Broadway and of the Nederlander organization.
Almost all the major musical hits of the last three years - ''Les Miserables,'' ''The Phantom of the Opera,'' ''Jerome Robbins's Broadway'' - have been performed in theaters owned by the Nederlanders' chief rival, the Shubert Organization. Like the Shuberts, the Nederlanders sometimes produce their own shows to help keep their theaters lighted. But in contrast to the Nederlanders, the Shubert Organization has plays or musicals in 11 of its 17 theaters.
The Nederlander organization has 12 Broadway theaters. Two of them, the Harris and the New Amsterdam, are on 42d Street and were operated as movie houses for many years. Their future is closely tied to the ambitious Times Square redevelopment project, in which several huge office towers and a merchandise mart are to be built on the seedy block and six other theaters are to be renovated.
Plans call for the Harris to be turned into a small 499-seat Broadway house and the New Amsterdam to be restored as a big musical theater. The non-Nederlander theaters to be renovated - the Liberty, the Victory, the Lyric, the Times Square, the Apollo and the Selwyn - would be controlled by a nonprofit organization called the 42d Street Entertainment Corporation, which would be a subsidiary of the quasi-public corporation managing the Times Square redevelopment project. Waiting for the Project
Mr. Nederlander said he was waiting for the much-delayed project to go ahead before he renovates and reopens his theaters.
''We've been ready for several years,'' he said, ''but there's no sense fixing those theaters up until the city starts tearing those other buildings down.''
''We're not going to do anything until we're assured that the project is going to go forward,'' Mr. Rubin said, ''because otherwise, if I fix those theaters up and spend a couple of million dollars, who's going to book them?''
Bookings, of course, are a problem now, but Mr. Nederlander said he was confident that if the two theaters are renovated he will be able to fill them. ''This business is cyclical,'' he said. ''Something will come along. Something always comes along.'' Long the Avis to the Shubert Organization's Hertz, the Nederlanders have sometimes co-produced plays with their rivals, most recently ''Les Liaisons Dangereuses'' and ''Nicholas Nickleby.'' But more often than not they have been competitors.
