Lennon was still not satisfied with the feel of the track, and several sound effects were taped, including 15 seconds of humming and a guitar and a harp-like sound, both to be played backwards; however, none of these were used on the released version. The track was mixed to mono and put aside as the group had decided to release "Lady Madonna" and "The Inner Light" as the single. On their return from India, the group set about recording the many songs they had written there, and "Across the Universe" remained on the shelf. In the autumn of 1968, the Beatles seriously considered releasing an EP including most of the songs for the "Yellow Submarine" album and "Across the Universe", and went as far as having the EP mastered.