The thumping rhythm and high-pitched voices of the Isley Brothers filled the stately courtroom in U.S. District Court yesterday as the jury listened intently to a tape recording of "The Pride."

Judge June L. Green leaned forward rigidly, also listening, a pale green kerchief knotted primly over her black robe. A young woman juror in a pink pant suit began to rock gently to the embracing soul music. A curly haired man tapped his knuckles against his chair. Other, older jurors stared stiffly at the tape deck and speakers mounted on the prosecutor's table.

O' Kelly Isley, one of the Isley Brothers, sat in the witness chair. Massive and bearded, he listened to the familiar words, nodding his head slightly:

Politician come to power, take it slow,

People need what you know.

You're a leader so you have to play along.

Show the hand, right or wrong.

Copyright by T-Neck Records, 1977.

It was not your ordinary court procedure, to say the least. But this has not been your ordinary trial.

Two men are on trial charged with the copyright infringement and interstate transport of more than 1,800 pirated or bootleg tape casettes of numerous popular songs including the Isley Brothers' "Pride."

The two men were arrested last summer in connection with th joint FBI-D.C. police "Triconn" phony fencing operation here, similar to the celebrated "Sting" operation two years earlier.

O'Kelly Isley, the fabled singer and secretary-treasurer of T-NECK Records in New York, came to Washington yesterday to testify to one simple thing. The eight-track tape containing "The Pride" that was played in court had not been made by his company or by CBS, which has a licensing agreement to reproduce it as well.

"Is that a pirated tape?" asked Assistant U.S. Attorney Stephen R. Spivack.

"Yes, it is," said Isley.

How does distribution of such pirated tapes affect you, Isley was asked by Spivack.

"It hurts me moneywise - a lot of it," Isley answered.

How much? "Two million dollars," said Isley without hestitation.

That is the figure, he said, a licensing agreement would have cost recording company in mid-1977, when the Isley Brothers' album "Go for Your Guns," which includes "The Pride," was at its peak of popularity and when the two defendants are alleged to have sold the unlicensed, pirated copies of it to an undercover FBI agent in the Triconn operation here.

The defendants, Leon H. Wais, 56, a manufacturer of jogging shorts in Baltimore, and David L. Whetzel, 35, who specializes in buying up inventory from closed-out and bankrupt business in Winston-Salem, N.C., deny the charges.

Defense attorneys will present their case next week. Prosecutors claim Whetzel provided the pirated tapes and Wais helped arrange the sale in two transactions last summer with a man who turned out to be undercover FBI agent William Gandy.