The song was one of the first pop singles to use flanging, an effect that can be heard in the bridge section after each chorus. Most sources credit the use of the effect to Olympic Studios engineer George Chkiantz who showed it to the Small Faces regular engineer Glyn Johns; he in turn demonstrated it to the group, who were always on the lookout for innovative production sounds, and they readily agreed to its use on the single. Although many devices were soon created that could produce the same effect by purely electronic means, the effect as used on "Itchycoo Park" was at that time an electro-mechanical studio process. Two synchronised tape copies of a finished recording were played simultaneously into a third master recorder, and by manually retarding the rotation of one of the two tape reels (flanges) using the fingers, a skilled engineer could subtly manipulate the phase difference between the two sources, creating the lush 'swooshing' phase effect that sweeps up and down the frequency range. Because the original single version was mixed and mastered in mono, the flanging effect in "Itchycoo Park" is more pronounced in its original mono mix, and is noticeably diluted in the subsequent stereo mix.