Article: Let It Be
Section: Concept

Question: Which producer/engineer did McCartney invite to contribute to the recording?

By late 1968, more than two years after the Beatles gave up touring, Paul McCartney was eager for the group to perform live again.
The sessions for that year's "The Beatles" (commonly known as the "White Album") had seen a number of serious arguments and strained relations among the group.
McCartney felt that the group's cohesiveness had been lost through years without playing live, and from using the studio not to record ensemble performances but to make increasingly complex recordings made up of parts played individually by each Beatle as overdubs rather than as a group.
He believed that the best way to improve band relations and revive enthusiasm was to get the group back into rehearsal as quickly as possible (the "White Album" sessions having only been concluded in October 1968) and begin work on a new album that made little or no use of studio artifice or multiple overdubbing.
This would allow the group to return to their roots by playing as a true ensemble, perhaps recording some or all of the new album during a one-off live concert or full concert tour.
This idea mirrored the "back to basics" attitude of a number of rock musicians at this time in reaction against the psychedelic and progressive music dominant in the previous two years.
McCartney believed that a return to live performance would reinstill the same sort of ensemble spirit and sense of unity that they had in their early years together.
McCartney also decided to invite producer/engineer Glyn Johns to contribute to the recording.
His proposed role was apparently not clearly defined, as McCartney also wished to retain the services of George Martin.
As a result, Johns was not entirely sure whether he was supposed to be producing (or co-producing) the album or merely engineering it, with Martin having no clear idea of where he stood either.
The other three Beatles were less enthusiastic about McCartney's proposals.
They had just completed five months' work on their previous album and were skeptical about the prospects of returning to live performance.
George Harrison in particular was very opposed to the idea of touring, having taken the strongest dislike out of any in the group due to the grueling tours of the Beatlemania era.
However he had recently enjoyed a series of jam sessions with Bob Dylan and the Band in the US, rediscovering his liking for straightforward ensemble playing, and he was attracted to the idea of the "back to basics" approach.
The same approach greatly appealed to John Lennon, who had grown increasingly wary of what he regarded as the excessive technical artifice used on their recordings since "Revolver" and had also made a recent return to no-frills ensemble playing in the shape of an appearance on "The Rolling Stones Rock and Roll Circus".
In addition, all the group members had greatly enjoyed the recording of Lennon's song "Happiness is a Warm Gun" during the recent "White Album" sessions which, due to its multiple sections and myriad time signature changes, had required the Beatles to focus sharply and revive their ensemble playing skills to lay down a coherent basic rhythm track before any overdubbing could be applied.
In the end, the group agreed to convene for rehearsals immediately following New Year's Day 1969 to begin work, even though no suitable conclusion or even firm direction for the new project had been agreed upon.