Specifically in their Abby Road album The Beatles used a technology that is found literally everywhere nowadays called stereo audio. Stereo sound is the illusion of sounds emerging from different directions, with some coming from the listener’s left and others coming from the right. In mono, all sounds are always centered. Before this album all their others were just mono. Stereo sound just makes the listening of the music all the more immersive. It is a really simple and basic feature but still pretty cool if you use it effectively.