This is the album where Jeff Lynne finally found the sound he'd wanted since co-founding Electric Light Orchestra three years earlier. Up to this point, most of the group's music had been self-contained – Lynne, Richard Tandy, et al., providing whatever was needed, vocally or instrumentally, even if it meant overdubbing their work layer upon layer. Lynne saw the limitations of this process, however, and opted for the presence of an orchestra – it was only 30 pieces, but the result was a much richer musical palette than the group had ever had to work with, and their most ambitious and successful record up to that time. Indeed, Eldorado was strongly reminiscent in some ways of Sgt. Pepper's Lonely Hearts Club Band.
Electric Light Orchestra's third album showed a marked advancement, with a fuller, more cohesive sound from the band as a whole and major improvements in Jeff Lynne's singing and songwriting. This is where the band took on its familiar sound, Lynne's voice suddenly showing an attractive expressiveness reminiscent of John Lennon in his early solo years, and also sporting a convincing white British soulful quality that was utterly lacking earlier. The group also plugged the holes that made its work seem so close to being ragged on those earlier records. "Showdown" and "Ma-Ma-Ma Belle" (the latter featuring Marc Bolan on double lead guitar with Lynne) became AM radio fixtures while "Daybreaker" became a concert opener for the group and, along with "In the Hall of the Mountain King," kept the group's FM/art rock credentials in order.