They played and recorded old classics, blues & Rock 'n Roll standards, some old Beatle songs (both released and unreleased.
One of those songs is called "Watching Rainbows". It is a playful, jammy track from the Let It Be sessions, and would eventually mutate into the final album's "I've Got a Feeling."
John's lyrics sound improvised, and there is even a reference to "I Am the Walrus."
Instead of watching rainbows I'm gonna make me someInstead of watchin' rainbows I'm gonna make me someStandin' in the garden, waitin' for the English sun to come and make me brown so I can be someone