Independent record company RMA said it would put unreleased tracks by musician Prince on sale to mark his death anniversary on April 21, Reuters reported on Wednesday. Of the six unreleased tracks, Deliverance was put on iTunes and Apple Music on Tuesday, while five other tracks are scheduled for release on April 21 and a disc version on June 2.

The musician recorded the six songs between 2006 and 2008 with his colleague Ian Boxill, who completed the project, RMA said. “I hope when people hear Prince singing these songs it will bring comfort to many,” Boxill said in RMA’s statement.

The statement said the late artist had created the music as an independent musician protesting against, what he considered, an “unjust industry”. His musical legacy has been estimated to exceed $500 million.

Prince was found dead in his home on April 21, 2016, days after his private jet had made an emergency landing because he was unwell. Some reports suggested that his flight was forced to land because of a drug overdose. Investigators found that Prince had been struggling with an addiction problem before he died. In June 2016, tests confirmed that he had died of an accidental overdose of a powerful opioid.