Cassette tapes offer committed music fans an intimate listening experience, although their introduction in the early 1960s was first touted as a way of improving recorded sound. By the 1970s, cassette players become commonplace, peaking a decade later with portable devices such as the Sony Walkman. The compact disc's popularity has since pushed cassette sales into steep decline. However, cassettes remain popular for those who listen to punk and religious music--and police interrogation rooms.
Like the reel-to-reel technology that they superseded, cassettes are simply another way of preserving recorded sound on magnetic tape. Then and now, the experience requires popping a plastic cassette into some type of playback device--usually, a tape recorder, stereo or boom box. The cassette case, or "shell," contains magnetic tape that is cut to pre-set lengths and winds around two spools.
The cassette is pushed into the playback area over two special playback heads and two spindles at the bottom, which keep it locked in place. Pressing on the "Play" button helps to rub the right playback head against the tape. This motion, in turn, produces an electromagnetic pulse that rearranges the particles into recognizable sounds.
Cassettes are considered more resistant to dust, heat and shocks than compact discs, and their various maximum lengths of 60, 80, 90 and 120 minutes offer more flexible playing times than their digitized counterparts. A cassette's contents can be easily replaced, too, by pressing the "Record" and "Play" buttons together to activate the erase head. This action purges the tape of its previous contents.
Cassette shelf lives peak at roughly 20 to 30 years, because the special magnetic oxide coating that enables the tape to play begins to flake off. The tape is also being stretched and pulled, making it more likely to break after prolonged use. The advent of digital voice recorders--which boast hundreds of hours in audio storage capability, without relying on magnetic tape--has also effectively wiped out the advantage once claimed by regular cassettes.