Tony Velo of Richmond and Ben Bishop of Rockville won semifinal matches yesterday to advance to to-day's final of the Middle Atlantic Lawn Tennis Association championships at Aspen Hill Racquet Club in Silver Spring.

Velo, seeded 16th, served 10 aces in beating Alexandria's El Motaz Sonbol, 4-6, 6-4, 6-2. Sonbol, 42, is the sixth seed and a former Davis Cup player from Egypt.

In the other semifinal, Bishop mixed his shots well in defeating Rich Pollara, 6-3, 7-5.

Sonbol, a clay court tactician, made only four unforced errors in the first set. He tracked down every shot, at times sliding four or five feet on the clay-like surface, always keeping the ball in play with soft pinpoint underspins on the backhand and a flicking topspin forehand.

Velo, former No. 1 at the University of Richmond, started the second set by breaking Sonbol's serve. Sonbol broke back and held his own serve to take a 3-1 lead, then Velo began to blast forehands into corners and serve with authority.

"That was the turning point," Velo said. "I had to start going for more winners from the baseline and wait for Sonbol to hit shallow so Ic ould come to the net. It was no use rallying with him. His strokes were too deceptive. I also had to got for broke on my serves."

The big 6-foot-4 right-hander blasted hiw way to 5-4 and served for the second set. He ripped three aces down the middle and a service winner to force the match into the third set.

Velo continued the power display, taking a 2-0 lead on overhead slams and forehand winners. Sonbol held serve twice while Velo built a 5-2 lead. Velo ended the match with three aces and an uncharacteristic drop volley.

Bishop, a 30-year-old tennis instructor at Indian Spring Country Club, is the eighth seed. He breezed in the first set by hitting rolling top-spin and heavy backhand underspin. He consistently hit backhand down-the-line passing shots to offset the aggressive serve-and-volley game of Pollara.

Pollara, the 15th seed, was trailing, 2-0, in the second set when he volleyed his way to a 5-4 lead, breaking Bishop's serve for the first time in the match.

Bishop seemed to lose concentration in the middle of the second set, but he held serve to 5-5 before breaking Pollara's serve and serving for the match. Bishop outstroked Pollara in the last two games to take the victory.

"I tried to make him hit that wide-angle sliced backhand either short or into the net," Bishop said. "At 6-4, he can reach lobs on any regular shot so I had to pull him out wide. It's just high-percentage tennis." CAPTION: Picture, Ben Bishop reaches for 6-3, 7-5 MALTA semifinal win over Rich Pollara. By Fred Sweets - The Washington Post