John produced several albums himself but he also relied on producers' talents to make decisions for him. In alphabetical order:

Neil Ardley
Peter Barber-Fleming
Guy Barker
Chris Blackwell
Wim Bloemendaal
Andrew Boland
Joe Boyd
Jerry Boys
Matt Butler
Phil Collins
Gerry Conway
Mark Cooper
Spencer Cozens
Serena Cross
Pete Dauncey
Norman Dayron
Doublas Eadie
[Rob Fraboni]
Malcom Gerrie
John Grimes
Jeff Griffin (BBC)
Cari Hamblett
Nic Harcourt
Reginald Hastings
Joe Hennessy
Jools Holland
Burkhard Hopper
Theo Johnson
Paul Kossoff
Martin Levan
Bill Levenson
Valda Lewis
Leo Lyons
Marc Marot
John McCoy
Jacqui McShee
Ralph McTell
Anthony Minghella
John Muir
Michael Norton
[Robert Palmer]
John Peel
Tony Phillips
Gary Pollitt
Bob Potter
Anthony Pugh
Sandy Roberton
Jack Ruby
Peter Rüchel
Pat Rush
Sister Bliss
Bram van Splunteren
Bridget St. John
Paul Stacey
John Stevens
Al Stewart
Peter Swettenham
Stefon Taylor
Jim Tullio
Louis Verschuur
Graham Walker
Teresa Walsh
John Walters (BBC)
Peter Watts
Reinout Weidema
Tony Wilson (BBC)
Andrea Wonfor
John Wood
Trevor Wyatt
Gabriel Yared
Brian Young

The Scotsman (25 April 2001) carried some nice quotes from Brian Young, owner of CaVa sound studios in Glasgow, who worked with John on Sapphire, Piece by Piece, the Apprentice, Cooltide and The Church With One Bell:

"In 1990, CaVa was voted the second-best recording studio in the world, pushing Madonna’s studio into third place. 'When I realised I could make a living, I began with a Revox two-track tape. I moved to a 24-track, which cost me £ 50,000 in 1979. Now, a young guy can spend £ 3,000 on equipment that fits in his room. Naturally, it is not as good as our stuff, but it’s adequate. He can get a CD manufacturer to make 1,000 discs for £ 800.'
"It means there is a lot more produced and while much is rubbish, the technology has changed things forever. It has made little difference to personalities. Without giving too much away, it is still a matter of some very big egos getting together. However, John Martyn is a joy. He’ll work for a week on a track and then re-do it because he’s heard something he likes better. He’s so professional, a modern trait.'"