When my son Cameron was about six or seven, he began nosing around in my Beatles books, and saw some of the recording credits. “How could Paul play bass, piano, and organ on the same song?” he asked. “He didn’t have six hands.” Most people with a passing interest in record-making are aware of the concept of overdubs, but I’ll throw out a quick description…

In the early days of recording, the idea was to capture a performance as it happened. The band set up, the recording engineer plopped down a microphone, and they played. If there was a screw-up, they took it from the top. If a singer or instrumentalist needed to be louder, they moved closer to the microphone.

Beginning in the 1960s, thanks primarily to The Beatles’ studio innovations, the whole philosophy behind recording changed. It was no longer about capturing a performance as it happened…