Organist Matthew Fisher has won a share of the royalties of A Whiter Shade of Pale - 42 years after the song became one of the biggest hits in pop history.
Lawyers said the ruling from the House of Lords could cause a copyright headache for major artists with musicians who performed on successful recordings lining up to bring claims for their contributions.
Fisher, 61, from Croydon, south London, who now works as a computer programmer, said he was "delighted" at the decision.
He launched his claim against the lead singer of Procol Harum, Gary Brooker, in 2005.
The group's record was released in 1967 and became the anthem of the Summer of Love. It was recently named as the most played tune in public places. But from 2005 it was the subject of a bitter legal battle between Brooker, who owned the copyright to the music, and Fisher, who wrote the haunting organ introduction and counter melody.
Fisher successfully claimed a share of the royalties from the tune after winning his claim in the High Court in 2006. He was awarded 40% of the music royalties.
But two years later Brooker was successful at the Court of Appeal where judges said Fisher, although a co-author, had no right to royalties because of the time that had elapsed before he made his claim.
On Thursday, the Law Lords reinstated the High Court decision, ruling that the delay in bringing the claim had not caused any harm to Brooker, who had benefited financially from the delay. However, Fisher can only claim future royalties from the record.
The organist, who watched the judgment being delivered from the Strangers Gallery overlooking the Chamber at the House of Lords, said he was "delighted" with the result and he had now won the recognition he believed he deserved for his part in the record.
He added: "This was never about money. There will not be a lot of that anyway. But this was about making sure everyone knew about my part in the authorship. A win without money was never going to be recognised as a win at all."
