All the takes they did, the instruments used, like the Mellotron and the final splicing of two versions with different tempos that John wanted for the final cut. That George Martin exclaimed was impossible but John said he had faith he could. And he and his engineer partner did. Today would be easily done with digital recording but then it was literally cutting audio tape and matching the point in the song seamlessly.
Nothing to get hung about mate. Strawberry Fields Forever.