Realtors gathered for their annual convention here this week were told that the growing sophistication of real estate sales and the increasing concentration of the industry into a few large companies could force independent Realtors to either specialize or get out of the business

Speaking to a packed session of occasionally angry independent Realtors, Coldwell Banker's senior vice president, Chandler Barton, told them that if they focused their efforts on a small specialized market, they would be able to keep the large and growing giant real estate companies at bay.

"There's plenty of business out there for all of us," said Barton. "But you will need to concentrate your abilities on one thing and not attempt to be all things to all people."

Albert J. Mayer, owner of Theodore Mayer & Brother Realtor Inc. of Cincinnati, told the group that as of the end of last year, 78 percent of the real estate firms in the United States were still small independents, companies with 10 sales agents or less. But, he said, the giants -- companies of 50 sales agents or more -- control 38 percent of the sales agents working in the United States, even though the firms make up only 3 percent of real estate companies. He said that 19 percent of the companies are middle-sized.

Mayer said that the companies most threatened by the growing giants are the medium-sized regional firms.

"There is room for the big companies and room for the little companies, but there's no room in the middle," said Mayer. "Small companies can offer personal service while staying flexible enough to be able to pull back during the hard times. The medium companies, however, don't have either the resources to compete with the giants or the flexibility to pull in their horns when they need to."

Mayer said that he sold the residential sales side of his medium-sized firm in 1979 because he said the cost of competing with newly opened Coldwell Banker offices in his area "would not be worth the risk." He said he is now concentrating only on commercial real estate sales.

"If you can specialize and narrow your focus, you can probably survive," said Mayer. "Find a market niche and concentrate your efforts there, so that by the time the giants come to town, you will have that niche locked up tight."

Mayer said he knew of one small independent firm that had decided to specialize in selling Victorian homes.

"Sure, it's a narrow market, but they own that market," said Mayer. "When someone wants to sell a Victorian home in that town, they go to them."

Realtors at the session, however, said they were concerned that finding a specialized niche could be difficult for many of them.

"It scares me that someone like Al Mayer is running scared," said a broker from Georgia. "We're being asked to make a lot of changes in our business in a very short time, and it's not going to be easy."

A dominant theme at this year's Realtor convention, attended by 25,000 members of the National Association of Realtors, has been the growing pressure for innovation and reorganization of the real estate sales industry. More than 60 percent of the exhibitors at the convention were computer companies peddling systems for real estate firms, and the best attended sessions were classes on the developing technology for the industry.

Kevin E. Villani, chief economist for the Federal Home Loan Mortgage Corp., told the Realtors that he predicts it will soon be possible to close a real estate transaction -- from contract to sale -- in less than two weeks. The process takes approximately six weeks today.

"You will be able to display electronically in your office or car all the housing data your client wants to see, including mortgage finance options," said Villani. "You will be able to accept the homebuyer's loan application and prequalify that borrower for a loan before the bid on the house is even placed."

Villani said the lenders will also be tied to the system and will be able to sell the loan on the same day.

"The system will underwrite the loan and even appraise the property," said Villani. "It will calculate the annual percentage rate, closing costs and all other information needed for developing and printing out the relevant forms."

Villani even suggested that there could soon come a time when real estate brokers would originate loans themselves.

"Once you tie the system together electronically, you put the tools for loan origination in the broker's office," said Villani.

The pace of change in the real estate sales industry is likely to accelerate through the '80s, said National Association of Realtors executive vice president Jack Carlson, and Realtors need to be prepared.

"The real estate industry has gone through a revolution in the last five years," said Carlson. "The skills required today are probably 300 percent higher -- and different -- than five years ago. And that will only continue."