Over the years, portable audio or media players have become increasingly more popular and are some of the more commonly owned electronic consumer products.  Portable players are used in any number of different settings.  For example, many people use portable players while exercising, e.g., outdoors or in the gym, and many use the players while commuting or walking between locations. 
Generally, a portable audio player is a personal mobile device that allows the user to listen to recorded audio while mobile.  A personal player refers to a portable audio player that is listened to with headphones.  Many times, these players also can receive broadcast radio signals, such as AM and FM signals. 
One of the first portable players that enjoyed widespread success was a compact cassette player, such as the Sony Walkman introduced in 1979.  As technology advanced, different types of portable players became popular and mainstream.  For example, compact disc players that played commercial CDs enjoyed success and the later models were able to play recordable CDR and CDRW media.  The next breakthrough in technology resulted in digital audio players becoming available.  The players were based on flash memory or hard disk storage.  Files were usually compressed using lossy compression; this reduces file size at the cost of some loss of quality.  The advantage of solid-state digital audio players over hard disks and CDs is resistance to vibration, small size and weight, and low battery usage. 
Digital audio players are designed so that a user can download content into the memory of the player.  The audio content of the player is therefore dynamic and can be easily changed by the user by simply deleting files that the user is no longer interested in and/or downloading new files.  The player typically includes a display screen, such as an LED screen, which displays certain information, such as the track number, the name and/or selection being played, radio station, etc. 
These type of players are thus of a type that the consumer has access rights and where the content storage is dynamic and can be changed by the end user.  The players can be worn on the body by using a strap, belt or the like. 
Nonprogrammable (closed) players can also come in different forms, such as an electronic greeting card.  The card will typically play a song, such as Happy Birthday, when the consumer opens the card.  The card has a micro speaker, a coil cell and simple leaf switch that opens and closes the circuit based on the opening and closing of the greeting card itself.  However, this type of device is not intended to be worn and function as a media player for the listening pleasure of an end user.