Many people contributed minor performances to many Beatles recordings, but assistant Mal Evans is responsible for some of the most recognizable sounds and performances of all.
You Won't See Me - organ. At Paul's direction, Mal played the distinctive single organ notes. Paul showed Mal where the notes were on the organ and then nodded his head when he wanted Evans to play, and shook it when he wanted him to stop.
Yellow Submarine - vocals on the chorus
Being For The Benefit Of Mr. Kite! - harmonica
A Day In The Life - alarm clock and piano. Evans controlled an alarm clock; counting the measures in the original 24-bar pause which can be heard clearly on Anthology 2. He was one of the five piano players simultaneously hitting the last chord of the song.
You Know My Name (Look Up The Number) - gravel and vocals. Mal contributed background vocals and stirred a bucket of gravel (as part of the rhythm).
Dear Prudence - tambourine
Helter Skelter - trumpet. He played a double solo with Lennon even though neither was proficient on the instrument.
Birthday - hand claps
What's The New Mary Jane - sound effects.
Maxwell's Silver Hammer - anvil. Ringo could not lift the hammer high enough to get the right sound and keep in time with the song.