Sony’s Walkman portable audio cassette player in 1979 improved on the transistor radio by allowing people to take their preferred music wherever they went (engineer Nobutoshi Kihara supposedly invented the device so that Sony co-chairman Akio Morita could listen to operas during long flights). But the digital revolution in personal audio technology was another two decades in the making and had implications beyond both the personal and audio.

Portable music went digital in the 1980s with the rise of devices built around CDs, mini discs and digital audiotape. In the 1990s the Moving Picture Experts Group (MPEG) developed a standard that became the MP3, a format that highly condenses audio files by discarding imperceptible sounds (although discriminating audiophiles tend to disagree with that description).

The Eiger Labs MPMan F10, which hit the market in 1998, was the first MP3 player to store music on digital flash memory—a whopping 32 megabytes, enough for about half an hour of audio. A slew of similar gadgets followed, some of which replaced the flash memory with compact hard drives capable of holding thousands of songs. The breakthrough product was Apple’s 2001 iPod. Technologically, it was nothing new, but the combination of its physical sleekness, its spacious five-gigabyte hard drive and its thumbwheel-based interface proved compelling. Today digital players are as likely to hold photographs, videos and games as music, and they are increasingly often bundled into mobile phones and other devices.

MP3s —immaterial and easily copied—freed music from the physical grooves in vinyl or plastic media. They also dealt a severe blow to the recording industry, which long resisted selling MP3s, prompting music lovers to distribute files on their own. Since 2000, CD sales plummeted from $13 billion to $5 billion, according to the Recording Industry Association of America. Meanwhile digital downloads rose from $138 million in 2004 to $1 billion last year; however, says Russ Crupnick, a senior industry analyst at NPD Entertainment, peer-to-peer shared files outnumber legal downloads by at least 10 to one. Looking ahead, he believes music will not be something to possess at all: the industry’s salvation (if any) may come from paid access to songs streaming from the Web.