AC DC frontman Brian Johnson signed on for another band world tour after ailing bandmate Malcolm Young urged him to "keep making music".

The British rocker was considering retirement from the road at the end of the group's last global trek but bassist Young's battle with dementia gave him the impetus to carry on.

He tells, "Malcolm did say one statement and when Malcolm speaks you usually listen. He said, 'Keep making music'. He knew what was happening."

Young was forced to sit out the recording of the band's latest album when his health issues took over his life and he's now in a care home.

Johnson insists the group's upcoming Rock or Bust tour will not be a memorial for the missing bandmate, who has been replaced by his nephew.

He adds, "He's the hardest man I've ever met in my life... and the straightest shooter I've ever talked to in my life. He didn't stand fools gladly and he just said what he meant, and what he said usually meant a lot. There was no softness. He didn't want any memorials - just keep making music."