The first popular magnetic recording technology was reel-to-reel tape. Developed in the late 1940s, and popularized by Ampex, the first commercial devices were released in 1948. Portable reel-to-reel devices remained large, limited by the size of the ¼ inch tape reel, though Kudeski S.A.'s Nagra SN recorders were substantially smaller. Originally developed for the US secret services and commercially available in the mid-1960s, Nagra SN recorders used 1/8 inch tape.

4-track and 8-track players meant re-arranging albums - and you couldn't rewind.

One portable media player that has become almost synonymous with failure is the 8-track tape. Unfairly seen as the Edsel of modern audio, the 8-track survived well into the 1970s, and was actually a commercial success. Using an endless loop of tape in a cartridge, 8-track was designed by Bill Lear. Lear may be best known for his eponymous business jets, but his engineering life began at Galvin Manufacturing Corporation, and he's also credited with being the developer of the original Motorola car radio. 8-track was intended as a replacement for Earl "Madman" Muntz's 1962 4-Track Stereo-Pak "CARtridges" and added improved pinch rollers to maintain tape tension. Rewinding was impossible, though fast-forward mechanisms became common. Ford backed the technology, and 8-track quickly replaced 4-track. Each tape cartridge had four programs of up to two tracks each, and could hold an entire LP album, though fitting an album onto the tracks could lead to odd track orders, and to silent sections which offended some listeners.