George Harrison filled up the two remaining tracks of the four-track tape by recording two backwards guitar solos, in a session which began at 9.30pm and ended at 3am the following morning.
The parts were worked out carefully, and appeared in at least five places during the song, although different mixes featured only some of them. None of the officially-released mixes contain all five.
The first guitar part was clean, and the second distorted. Both solos were merged into one during a reduction mix created the following day, to make way for vocal overdubs.
Listen to the section of the song containing the main solo reversed, to hear how the guitar sounded as it was recorded: