# Cassette and Walkman Anatomy How a Compact Cassette and a Sony Walkman turn magnetised tape into music, part by part By Numa Topic: Art, Music & Film [Open the interactive Jig](https://ask.jig.com/j/mytaZTmIdXPQ) ## Guide ### 1. A pocket full of music In 1979 the Sony Walkman let people carry their own music anywhere for the first time\. It plays a cassette: a small plastic case holding a long ribbon of tape\. Let's take both apart and see how a strip of tape becomes a song\. Drag to turn the view\. The first Walkman, the TPS\-L2, weighed about 390 grams without its two AA batteries\. ### 2. Inside the cassette A cassette is two plastic halves screwed together\. Inside sit two reels, called hubs, with tape wound between them\. The tape runs past little guide rollers and along the open front edge, where the player can touch it\. The tape is only 3\.81 millimetres wide, and a 60\-minute cassette holds about 86 metres of it\. ### 3. Music made of magnetism The tape is a thin plastic film coated with tiny magnetic particles, usually iron oxide\. Recording leaves a pattern of magnetised patches along it\. Here it is eight times bigger: four narrow tracks, two for each side of the tape, one for each ear\. Nothing is carved into the tape\. Patches packed close together store high notes; spread\-out patches store low ones\. ### 4. Into the Walkman Two spindles in the Walkman poke up into the reel hubs, and their teeth grip the hubs like keys\. The cassette's open edge now faces the machinery\. We have left the cassette's top half off so you can watch the tape\. The front wall of the Walkman is cut away here so you can see inside\. ### 5. Press play A small motor and a rubber belt spin a heavy wheel, the flywheel, which keeps the speed smooth and turns a thin steel shaft called the capstan\. Press play: a rubber pinch roller swings in and squeezes the tape against the capstan\. The capstan, not the reels, pulls the tape along at a steady speed\. Every cassette plays at 4\.76 centimetres per second, so one 30\-minute side uses about 86 metres of tape\. ### 6. The head listens The play head is a tiny electromagnet: a ring of iron with a coil of wire and a gap thinner than a hair\. As the magnetised patches slide across the gap, they make a small electric current flow in the coil\. That faint current copies the shape of the original sound\. The head's gap is about 2 micrometres \(thousandths of a millimetre\) wide, roughly 35 times thinner than a human hair\. ### 7. Two reels, two speeds The take\-up reel winds the tape in through a slipping clutch, a joint that gives way a little, so it never pulls harder than the capstan feeds it\. As its pack grows and the other shrinks, the reels change speed: the emptier reel spins faster\. The tape itself always moves at the same pace\. Watch the orange pack grow\. At the end of a side, the first Walkman simply stopped\. ### 8. Out through the headphones The head's signal is far too weak to hear, so an amplifier on the circuit board makes it about a thousand times stronger\. Wires carry it to the headphones, where it pushes thin speaker cones back and forth to shake the air\. The Walkman has no loudspeaker at all\. The first Walkman had two headphone sockets and an orange hotline button, so two friends could listen together and still talk\. ### 9. Flip to side B When side A ends, take the cassette out and turn it over\. Now the head meets the other two tracks and the tape runs the other way, so the second half of the album plays\. Press the button to flip it\. A 60\-minute cassette holds 30 minutes of music on each side\.