John Richard Baldwin Jones' collaboration with the Shadows nearly prevented the future formation of Led Zeppelin, when the parties engaged in talks about the possibility of Jones replacing their bassist Brian Locking, who left the band in October 1963, but John Rostill was ultimately chosen to fill the position.
In 1964, on the recommendation of Meehan, Jones began studio session work with Decca Records. From then until 1968, he played on hundreds of recording sessions. He soon expanded his studio work by playing keyboards, arranging and undertaking general studio direction, resulting in his services coming under much demand. He worked with numerous artists including the Rolling Stones on Their Satanic Majesties Request (Jones' string arrangement is heard on "She's a Rainbow"); Herman's Hermits; Donovan (on "Sunshine Superman," "Hurdy Gurdy Man," and "Mellow Yellow"); Jeff Beck; Françoise Hardy; Cat Stevens; Rod Stewart; Shirley Bassey; Lulu; and numerous others. As well as recording sessions with Dusty Springfield, Jones also played bass for her Talk of the Town series of performances. His arranging and playing on Donovan's "Sunshine Superman" resulted in producer Mickie Most using his services as choice arranger for many of his own projects, with Tom Jones, Nico, Wayne Fontana, the Walker Brothers, and many others. In 1967, Most, as music supervisor, also tabbed Jones to arrange the music for Herman's Hermits' theatrical film Mrs. Brown, You've Got a Lovely Daughter (film) , released in January 1968. Such was the extent of Jones' studio work – amounting to hundreds of sessions – that he said years later that "I can't remember three-quarters of the sessions I was on."
It was during his time as a session player that Jones adopted the stage name John Paul Jones. This name was suggested to him by a friend, Andrew Loog Oldham, who had seen a poster for the 1959 film John Paul Jones in France. He released his first solo recording as John Paul Jones, "Baja" (written by Lee Hazlewood and produced by Oldham) / "A Foggy Day in Vietnam", as a single on Pye Records in April 1964.
Jones has stated that, as a session musician, he was completing two and three sessions a day, six and seven days a week. However, by 1968 he was quickly feeling burnt out due to the heavy workload: "I was arranging 50 or 60 things a month and it was starting to kill me."
During his time as a session player, Jones often crossed paths with guitarist Jimmy Page, a fellow session veteran. In June 1966, Page joined The Yardbirds, and in 1967 Jones contributed to that band's Little Games album. The following winter, during the sessions for Donovan's The Hurdy Gurdy Man, Jones expressed to Page a desire to be part of any projects the guitarist might be planning. Later that year, The Yardbirds disbanded, leaving Page and bassist Chris Dreja to complete previously booked Yardbirds dates in Scandinavia. Before a new band could be assembled, Dreja left to take up photography. Jones, at the suggestion of his wife, asked Page about the vacant position, and the guitarist eagerly invited Jones to collaborate. Page later explained:

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