To be fair, such a digression could easily fill another 3-4 articles on its own.
Magnetic recording triggered the birth of the technique many (incorrectly) refer to as "sampling" today. (The term is "sample loops" or just "loops" – "sampling" refers to the process of recording the actual sounds digitally.) The looping of those sampled sounds underly almost all music today. It's most obvious in the work of Norman Cook, but even 'live' acts use it as a matter of routine now in their studio recordings.
This technique was first used in the 1940s and led directly to the "Musique Concrète" movement that was so influential on the likes of the BBC Radiophonic Workshop. Most of their output during the 1950s and '60s was Musique Concrète, albeit often with very early synthesised sounds added.
The term "loop" came from these pioneers: they had to do it the hard way, by recording sounds onto tape, re-recording them as many times as required onto another tape – at different speeds, in order to get the necessary notes – then chopping the resulting tape up into individual notes. (This was all worked out mathematically, hence the maths or engineering backgrounds of many of those involved.)
These individual snippets of sound – bass lines, rhythm / percussion cycles, even short sections of melody – were then joined together to form the necessary tape loops needed to produce the final piece. For example, the percussion sequence might be quite short and result in a fairly short loop of tape that could be repeated over the full track. (Most music is filled with repeated patterns and motifs. Listen to any dance track and it's pretty obvious, but you'll hear it even in Beethoven and Bach.)
A complex piece might require multiple, very long, loops of tape, all played in synchrony, with some loops so long that the team would have to jerry-rig a system of reels and pulleys to run the tape out of the machine, out of the door, down a corridor, and all the way back again.
Multiple tape machines were used for this. Even "bouncing" tracks is a term descended from this era.
Digital audio workstations ("DAWs") hide all the fiddly mathematics and tape editing today, but the underlying concepts and principles haven't changed.
Most of this can be gleaned from the BBC's own (belated) celebration of the defunct BBC Radiophonic Workshop: The Alchemists of Sound It's a shame the BBC never expanded it into a series covering the wider context of electronic music in general.