“In My Life” was written mainly by John Lennon and credited to Lennon–McCartney, the major song-writing duo of the Beatles. Later news reports showed that John Lennon wrote most of the song, and it is clearly “Lennon-ish”, but Paul McCartney and Lennon later disagreed over how much each of the two band members contributed to the song. It was mostly about the melody that they disagreed.
“In My Life” was originally recorded by the Beatles and released on the 1965 album Rubber Soul. The record producer, George Martin, contributed the electric piano solo bridge.
If I remember correctly, the electronic piano solo in the middle, added by Martin (who was a classically trained musician), was added during a lunch break when the band members were not around. Personally, it never sounded quite right to me, so I’ve taken the liberty of changing it a bit. I’ve also repeated the 2nd verse to make the piece a bit longer.
In this In My Life practice track the part labeled “lead” is meant to be sung, with the piano (called “Lead” here) coming in only where the singer is not singing. (Or perhaps the “lead” instrument could play the melody quietly along with the singer).
The practice track for BASS players is here.