Its haunting organ fused Bach with pop to create one of the most enduring hits of the flower-power era — and next week A Whiter Shade Of Pale returns to centre stage.

The Procol Harum song is at the centre of a million-pound royalties dispute to be heard at the High Court in London on Monday. Released in 1967, it became a global smash, selling 10 million copies. It is still used in advertisements and regularly features in “greatest song of all time” polls.

The song has always been credited to Gary Brooker, Procol Harum’s frontman, and lyricist Keith Reid. Now almost 40 years on, Matthew Fisher, the band’s classically trained organist, claims that the song’s signature winding melody line was his work. Fisher, 60, now a computer programmer in Croydon, South London, is claiming a share of the song’s copyright and past sales, which could earn him up to £1 million.

The dispute is complicated because all sides agree that Johann Sebastian Bach originally inspired the song’s mournful melody.

Brooker first wrote the song as a straight R&B tune, based on Bach’s Air from the Orchestral Suite No 3 in D (or Air on a G String), which he had heard on a Hamlet cigar advertisement, and the composer’s Cantata No 140, known as Sleepers Awake.

With Bob Dylan’s records then popularising the Hammond organ sound, the band called on Fisher to embellish the track, but the organist argues that his contribution was far greater. Musicologists will tell the court that he transformed the organ melody into something far superior to the chord structure that Brooker borrowed from Bach.

His organ melody includes lines running in counterpoint to the vocal melody and also the memorable eight-bar solo that appears between verses. He transformed the tempo and rhythm of the cantata “lift”, cleverly disguising its classical source.

Brooker, who strongly contests the claim, concedes that Fisher, who left the band in 1969, “refined” the song’s use of Bach. But the organist believes he created an original melody.

Fisher has hired Jens Hill & Co, the company that represented Pete Best when the axed Beatles drummer successfully sued his former bandmates for royalties. Brooker, 61, has engaged Harbottle & Lewis, which acted for Simon Fuller, the Pop Idol mogul, in a recent dispute with Simon Cowell. Brooker said: “A Whiter Shade of Pale was written by Keith and myself before Matthew even joined the band.”

He added: “I am shocked and dismayed that after Matthew had worked with us quite happily over the course of nearly 40 years without him once alleging that his role on Whiter Shade was anything other than as a musician, it is only now that he claims to recall ‘composing’ part of the song. I think people can draw their own conclusions from this.”

A keyboard will be installed in the High Court for Fisher to demonstrate his contribution, his solicitors said.

Fisher has rejoined Procol Harum on two occasions, finally parting company with the group in 2004. He issued a statement on his website rejecting allegations that his wife, Carol Bellantoni, an American artist, had in any way instigated the legal action and his departure from the band.

Procol Harum toured with Jimi Hendrix after the success of Whiter Shade. Their symphonic rock remained popular but the 1967 single proved to be their commercial peak.

It was named joint Best British Pop Single released between 1952-1977 (with Queen’s Bohemian Rhapsody) at the silver jubilee British Rock and Pop Awards.

Money Spinner

Sandi Thom references the song in this year’s No 1 hit I Wish I Was a Punk Rocker (with Flowers in My Hair)

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