When the transistor replaced the bulky and unreliable vacuum tube in amplification units, transistors did the job better and were much smaller, making it possible to drastically reduce the size of radios and record players.
Transistors also had significantly lower power usage which meant that batteries became an option as a power source. The first transistors were used in calculators but were very quickly applied to radios.
The transistor radio was announced on 18 October 1954, but they were not commonly available until 1955.
The transistor radio might not have had the sound quality of larger table-top models but it was portable and much cheaper. It was especially appealing to the young, and a 'tranny' became a necessary part of teenage culture in the late 1950s and 1960s.
Transistors were also used in car radios and small tape recorders, enabling people to take their entertainment with them wherever they went.
Now that it was no longer necessary to sit still at home to enjoy music, many young people heard popular songs first on transistor radios - and on AM radio as they cruised around in their cars.
Transistor radio became the major outlet for rock & roll and R&B, and by the 1960s successful record companies like Motown, and hit-makers like Phil Spector, were actually mixing their records to suit the low fidelity of these machines and thereby maximise their appeal to the kids.