Cambridge 1969

On the second of March, 1969 , Yoko was invited to perform at a "Natural Music" concert to be held at Cambridge University in Cambridge, England. The performance was recorded live from the Lady Mitchell Hall on the premises.
John had brought along his guitar - the Epiphone Casino - and his amp and was creating feedback in order to accompany the vocal talents of Yoko Ono. The entire performance would last over 20 minutes and other musicians on the track included John Stephens on cymbals and percussion as well as John Tchicai on the sax (both of whom come into the performance after about 15 minutes). This performance is completely undertaken as performance art and is faded out on the record ending with a lone sax improvisation.
The track can be found on side one of the Zapple LP/CD "Unfinished Music No. 2; Life with the Lions" by John and Yoko.

"Under The Mersey Wall" Session

When George Harrison was in Los Angeles back in November of 1968, he had shown interest in the Moog III synthesizer which was a gigantic patch cord affair (monaural key capability). This keyboard was demonstrated to him by Bernie Krause. Mr. Krause had been hired to play Moog on tunes for the upcoming Apple artist Jackie Lomax's LP (which George Harrison was producing). Intrigued by the machine, George asked that a demonstration of the machine and it's sound be shown and the demonstration was recorded. The tapes of the demo were kept by Apple. The track which would be eventually released as the A-side of the "Electronic Sound" LP was mainly white noise and bleeps. One of the synths was then purchased by George and shipped to his home in England - the synth would eventually be brought to EMI Studios and used on some of the "Abbey Road" sessions.
Fast forward to mid February 1969; Bernie Krause visits George at his home and learns that his demo back in November 1968 had been recorded and would be released as "No Time or Space" on a "Zapple" LP (a subsidiary to Apple). Of course, Mr. Krause disagreed and backed out of the project. George promptly removed the Bernie Krause credit from the back of the LP jacket before being printed.
The B-side to the LP was therefore recorded solely by George at his home. He named it "Under the Mersey Wall" and it consists of some musical phrases and experimentation played on the synth keyboard.
Eventually, both sides were officially released as the Zapple LP "Electronic Sound". On the US release, the side titles are switched so that the A-side plays the B-side and the B-side plays the A-side. This experiment was also released on CD back in 1996 and as part of the "George Harrison: The Apple Years"  box set from 2014 on a remastered CD with a nice gatefold cover showing the Moog keyboard and patches.
The LP didn't sell we, it wasn't promoted very well - typical of Apple Records at that time with non-Beatles produce. George Harrison himself hardly talked about it at all during his lifetime.

George Harrison Beatles Demos February 1969

On February 25 1969, George Harrison entered the EMI studios in London specifically to demo three of his latest (at the time) compositions. George had not contributed any songs for the rooftop session nor for the next day's basement session although several of his tunes were committed to tape during both the Twickenham rehearsals and the Apple Studios recordings during the "Get Back/Let It Be" session a month earlier. It also happened to be George's 26th birthday.
The new tunes included "Old Brown Shoe" (take 2) with George singing and playing piano. Two electric guitars were overdubbed as well. This demo can be heard on the commercial recording for the Apple 3LP/2CD "Anthology 3" project.
Up next is a beautiful version of "All Things Must Pass" (take 2); this consisted of George playing an electric guitar with the tremolo effect up full and vocal. A second vocal and plain electric without the effect was also added. There are two mixes available of this tune. One is on the bootleg "More Masters" which contains the second vocal - the other being the version on the official recording for the Apple 3LP/2CD "Anthology 3" project whereby there is only the single vocal.
Finally, the third demo consists of George's masterpiece "Something". The recording is built on an electric guitar and George's vocal. This version can also be found on the Apple 3LP/2CD "Anthology 3" project. All three tunes were mixed and given to George on acetates for him to take home.
As an aside, the George Harrison demo version of "Something" was most likely the demo given to Joe Cocker to record (as well as a demo of "She Came In through The Bathroom Window" which was also recorded by Joe). It's ironic that Joe Cocker recorded both songs in LA but that the songs were released after the issuance of "Abbey Road" in November 1969.