Before the invention of tape recordings and any type of sound recording material the only way for people to hear music was to either go out or play it yourself. Until 1878, when Thomas Edison made the phonograph, which was capable of recording sounds.

Before magnetic tape, artist would come into sessions live and the sounds would literally be etched into the disks. If they make mistakes then they would have to either deal with it or completely restart. Magnetic tape enabled much more vivid sounds that could be cut and spliced.

Les Paul was an innovator responsible for many major innovations  like electric guitar and later, Multi-tracking. Multi-tracking was the act of playing more than one track at once, forming a cohesive sound.

When 16-track came in people were able to over dub to their hearts content, comprisable to painting over a painting over and over to get the perfect look. Carti could make dark side of the moon but pink floyd could never make whole lotta red. Ampex 350 from 1965 is a recording device that could record on four tracks, and weighed 204 pounds, it costs 20k. The Tascam Teac 80-8 could record on eight tracks and weighted 75 pounds, it costs around 10k.