Yes album of "fresh" material was something he thought was too difficult to achieve, following the band's history of internal conflict. He aimed to present the "high technical edge" that Yes were known for, within the structure of more concise and direct songs and not spotlight only technical prowess. Anderson initially resisted this approach as he wished to distance himself from the more commercial music that had largely defined Yes across the previous decade. When recording began, Elias recalled a lack of solid material and the tension between Anderson and Howe especially, including the refusal of the two to stay in the studio while the other was present. Elias tried to help stimulate creativity and brought in a Hammond organ, but said Wakeman refused as he thought the instrument was outdated. Elias concluded that ABWH "didn't care about a note of music", and was relieved to have finished some of the material at all, considering the difficulties and his personal dislike for some of the songs. Matters complicated further when ABWH had started to put takes down. Wakeman and Howe had both agreed to solo commitments prior to recording, so their respective keyboard and guitar tracks were stored onto a computer, but not finalised and mastered. In their absence, Elias and Anderson brought in session musicians to play new arrangements from the initial takes as they were dissatisfied with what Wakeman and Howe had played. Elias said, "We weren't looking for only the early-'70s 'pyro technique'. We wanted something more modern". Among the 11 additional keyboard and synthesiser players featured on Union is Jim Crichton of Saga. Crichton and his assistant Brian Foraker were given songs that needed work and the pair "tried to fill in the gaps" at Crichton's own studio by playing parts that they thought Wakeman might play under those circumstances. Crichton felt "Dangerous" was a particularly strong track in demo form, but that the final version on the album was substandard. Rabin was invited to replace Howe's parts, but turned down the opportunity. Recordings were made with session guitarist Scott van Zen, but ultimately the parts in question were replaced by Jimmy Haun, who was suggested by Steve Porcaro and had worked in Squire's band The Chris Squire Experiment. Haun later said that it was Anderson, Elias, "and one other person" who made the final decision as to which parts were kept and replaced by someone