In the studios of EMI particularly in number 1 (the largest room) on March 31 1967 The Beatles entered and work was to continue on a John Lennon number entitled "Being For the Benefit of Mr. Kite". Starting at a session from March 28 1967:The basic track was taken off the shelves, dusted off and polished by adding some harmonica and organ at the beginning of the song for the intro - thickening whatever harmonicas were already recorded. Both harmonicas were played by Ringo and George although some sources also mention Mal Evans and Neil Aspinal contributing which is also possible. The middle of the song had some tambourine added by Ringo, a guitar added by Paul, organ by John and George Martin playing the cascading notes on another organ.
The next day on March 29 1967, it seems that John and George "thickened" up the harmonicas by adding a couple more blasts in the intro.The melody being carried at the last instrumental verse was being recorded on this day as well.
Finally, on March 31 1967, the tape loop consisting of various circus recordings and steam engine sounds being cut up and manipulated were added to the last instrumental verse. The final low chord on the organ and a bit of glockenspiel were also added to the tape to complete the song.
You can hear some of the take 09 overdubs with the tape loops, etc. on the commercial version of the Apple/EMI 2-CD/3-LP "Anthology 2" which actually cross-fades from take 07 without the overdubs to take 09 with the overdubs at around the two minute and a half mark.