with producer George Martin. Harrison perfected the part with the tape running backwards so that, when reversed, it would fit the dreamlike mood. One guitar was recorded with fuzz effects, the other without. Engineer Geoff Emerick described the meticulous process as "interminable". "I can still picture George hunched over his guitar for hours on end", Emerick wrote in 2006, "headphones clamped on, brows furrowed in concentration." During the break before the second bridge, the sound of a yawn can be heard, preceded by Lennon saying to McCartney, "Yawn, Paul." Release "I'm Only Sleeping" was first released on 20 June 1966 as the second track on the US album Yesterday and Today and on 5 August 1966 as the third track on Revolver, the album for which the song was originally intended. The US version of Revolver did not include the song as it had already been released: US Beatles releases frequently differed from the British versions. The mono and stereo versions of "I'm Only Sleeping" differ in the positioning and length of the backwards guitar parts: US mono version (mixed on 12 May 1966): No backwards track during the second verse but a quick fragment is heard on the "time" in "taking my time" and "ceiling" in "lying there and staring at the ceiling". The track is fully intact during the instrumental break and continues into the words "please don't" in "please don't spoil my day". Near the end of the song the backwards track starts four beats after the last word "sleeping". US rechannelled stereo version: This version was mixed from the US mono version of the song but has far more reverb. It was used only on the initial pressing of the Yesterday and Today album. US stereo version (20 May): Backwards track on "running everywhere at such a speed" and "till they find there's no need". The track fades in two bars into the solo but continues into the word "please" in "please don't spoil my day". At the end of the song, the track starts immediately after the word "sleeping". UK mono version (6 June): Backwards track on "where at such a speed", "there's no need" and "staring at the ceiling". The track stops at the end of the solo and at the end of the song, starts immediately after the word "sleeping". Of the five mixes of "I'm Only Sleeping", this version features the most