Some of music’s biggest names, including Chris Martin, Angelique Kidjo and Damon Albarn, have signed a petition calling for the release of Bobi Wine, a Ugandan MP and pop star.
The opposition politician, whose real name is Robert Kyagulanyi, has been in detention for more than a week.
The musicians have condemned his “vicious” treatment in custody.
Bobi Wine’s lawyers say he has been seriously assaulted in detention, which the military denies.
He is due to appear before a military court on Thursday to face charges relating to the illegal possession of firearms.
The petition was started by Rikki Stein, the former manager for Nigerian music legend Fela Kuti – a fearless critic of Nigeria’s military regimes during his lifetime.
“It’s like a re-run of Fela. He was often beaten for speaking out,” he told the BBC.
The more than 80 signatories also include Nigerian Nobel laureate Wole Soyinka, U2 bassist Adam Clayton, The Pretenders lead singer Chrissie Hynde and Genesis lead singer Peter Gabriel.