A day late and a dollar short — well, more like 13,000 days, and possibly millions of dollars.
In 2005, the guy who played the organ in Procul Harem’s 1967 hit A Whiter Shade of Pale filed suit against the lead singer. Matthew Fisher claimed he was entitled to an estimated $2 million in back royalties as a co-author of the song (his contribution being the famous organ solo).
Fisher won in the (UK) trial court, but the appeals court just reversed, saying that he was "guilty of excessive and inexcusable delay in his claim to assert joint title to a joint interest in the work …. He silently stood by and acquiesced in the defendant’s commercial exploitation of the work for 38 years.”
So despite being confirmed to be a co-author of the song, Fisher will get neither back royalties nor future royalties (unless he successfully appeals to the House of Lords).
If Fisher had been able to convince the court that he didn’t know he’d been left off the credits, conceivably he might have had a shot at getting future royalties, and perhaps back royalties for the statute-of-limitations period (probably three years in the U.S., although I haven’t looked it up).
But the way a NY Times blog describes the song’s credits, if he had made such a claim, he likely would have been laughed out of court: "music by Gary Brooker, lyrics by Keith Reid, it says on the band’s own recording and on the 600-odd cover versions that other artists have made over the years."