Members of American band Eagles of Death Metal testified Tuesday at the trial for the November 2015 attacks on Paris which saw gunmen attack the Bataclan concert hall while the rockers were playing.

Frontman Jesse Hughes and guitarist Eden Galindo arrived at the court complex in central Paris dressed in black suits before going on to describe how their gig six and half years ago changed their lives forever.

Hughes told reporters outside that he had finally forgiven the Islamic State extremists who killed 90 people at the concert during the worst terror attack on France in modern history.

"I'm a Christian and everyone can be lost and everyone needs to find the way and most of the gentlemen in there do, so I forgive them and I hope that they find the peace of God themselves," the 49-year-old told reporters.

France's biggest-ever criminal trial is hearing evidence against the only surviving member of the suicide team that targeted restaurants, bars, the national sports stadium and the Bataclan, leaving 130 people dead in total.

Salah Abdeslam, who was arrested in Belgium after five months on the run, has explained how he abandoned plans to blow himself up and has apologised to victims.

His tearful appeal for forgiveness last month contrasted with his defiance at the start of the trial when he refused to acknowledge the authority of the judge or answer questions.

Nearly 20 others are answering charges ranging from providing logistical support to planning the attacks, as well as supplying weapons.

Verdicts are expected on June 29.

Hughes told the court that he recognised the sound of gunfire instantly when the three gunmen with suicide vests burst in mid-show and said he "knew death was upon us".

"Nearly 90 of my friends were murdered in front of us," he said, referring to the fans killed.

US singer Jesse Hughes arriving at the court in central Paris US singer Jesse Hughes arriving at the court in central Paris Photo: AFP / Geoffroy VAN DER HASSELT

He fled the scene in a taxi with his girlfriend to the local police station, only later learning that the band's merchandising manager, Nick Alexander, was among the deceased.

But he said the attackers had not succeeded in their goal of depriving people of the joy they feel from listening to music.

"You can't kill rock'n'roll," he said, quoting fellow rocker Ozzy Osbourne.

After his brief appearance in the witness box, he embraced emotional witnesses and victims who were following proceedings during the packed hearing, ending up in tears himself.

"I have a great family of friends as the result of this. Quite possibly some of the most beautiful things I have ever seen has been the result of this," he told reporters after the hearing.

Galindo, 52, told the court the hard-rockers were enjoying a "great show" and he at first thought the gunfire was a sound system malfunction.

After describing his personal struggles since the attacks, he said he thought about the victims and their families every day.

"I'll never be the same," he said.

Hughes, who was a supporter of former US president Donald Trump, is a controversial figure in France after suggesting in the aftermath of the attacks that Muslim security staff were involved and that Muslims were celebrating outside the venue.

He was barred from the Bataclan re-opening concert in 2016 as a result.

He later apologised for his remarks and withdrew them, saying he had been struggling from nightmares and mental health problems at the time.

"Of course, I was waiting for this testimony and I was happy to see someone who is finally trying to find a certain form of inner peace, and it was a dignified testimony today," Olivier Laplaud, a survivor of the attack, told AFP.

Asked why he was now ready to forgive the attackers, Hughes told reporters: "I was never out of the mood of forgiveness. But I've just worked through it."