LONDON — The British soldier said to have been at the “very heart” of abusing detainees in Iraq enjoyed conducting what he called a “choir” of shrieking and groaning Iraqis, a court martial was told yesterday.

Corporal Donald Payne, who confessed to the war crime of inhuman treatment when the trial opened on Tuesday, was also said to have been the soldier who was shouting and swearing at detainees in a video recording shown in court.

Julian Bevan of the prosecution, said the “choir” consisted of Corporal Payne systematically assaulting each detainee in turn, either by hitting them in the stomach or punching them in the body.

This caused “each one to shriek out or groan in pain — their various noises, as a reaction to being struck, constituting the music.”

Mr. Bevan said Corporal Payne clearly enjoyed conducting the choir for the enjoyment and pleasure of those who visited the detention facility.

“It is significant that Corporal Payne’s abuse of these prisoners was done wholly openly, not only in front of soldiers that he knew but in front of total strangers,” he added. The court was then shown a one-minute amateur video recording in which a soldier identified by the government as Corporal Payne could be seen forcing some five groaning detainees to maintain the so-called “stress position.”

They were required to crouch with their backs to the wall and their arms outstretched.

In the video, a hooded prisoner who stands up is ordered by the soldier to “F—— get down” to the knees-bent position. When he then collapses, unable to hold the position any longer, he is told to “Get up, get up, f—— get up.”

The soldier, wearing a black T-shirt and desert combat trousers, is seen dragging a prisoner up when he fails to respond.

No beating or kicking can be seen but moans of pain are clearly audible. Another soldier made the video recording, Mr. Bevan explained.

“It seems that soldiers, when in Iraq, sometimes photographed or videoed incidents as keepsakes.”

The judge said sketches of the video could be published.

Evidence also existed, the court was told, that Corporal Payne had suddenly grabbed the head of a particularly difficult prisoner and beat it against the wall three times.

The detainee, a hotel worker named Baha Mousa, died shortly afterward of asphyxia and multiple injuries.

Mr. Bevan told the panel of seven officers trying Corporal Payne and six other servicemen in Wiltshire that they would have to decide whether his conduct “even begins to be acceptable.” Corporal Payne has denied the manslaughter of Mousa. He also denies perverting the course of justice by encouraging others to lie about how Mousa died.

Six other servicemen have denied charges of inhuman treatment, assault, and negligently performing their duties in connection with the questioning of suspected insurgents.