"Hey Bulldog" was entirely recorded on only one four-track tape.
This information was processed to a four-track tape (with the film's sound on one of the tracks), leaving Wonder space to add his own musical accompaniment.
The four-track tape, prepared by Ampex along with the reel-to-reel tape, has the songs in the original, chronological order.
It became available on other tape formats, including four-track tape (1966) and cassette as the formats developed.
They spent approximately 700 hours in the studio over 129 days, using four-track tape.
A four-track tape has four tracks all lying next to one another, like a highway with four lanes.
Cassettes move a four-track tape in either of two directions, corresponding to their side A and side B labels.
However, there is a kind of recording called quadraphonic that uses four-track tape to play four different tracks at the same time.
In the early days, Norwegian black metal songs were recorded on four-track tapes, but in recent times, the music has become more sophisticated.
This is the first Beatles album to be recorded entirely on four-track tape, allowing for good stereo mixes.