The MiniDisc (MD) player is one of those devices that seem to get unfairly discounted. What is a MiniDisc player? Back in 1992, Sony (co-creators of the compact disc) decided to replace the aging audiocassette with a new digital medium, a very portable analog to the CD. This gave rise to the MiniDisc, a small disc enclosed in a cartridge that can store near-CD quality music (sacrificing quality for extreme portability). While remarkably popular in Japan, sound quality problems in early models have given the MiniDisc player a bad rap on North American shores.
MD technology uses a form of compression known as Adaptive Transform Acoustic Coding (ATRAC), which produces audio data that is 1/5 the size of the original with very little loss in fidelity. Like MP3s, ATRAC uses psychoacoustics-based algorithms to filter out perceptually inaudible information. Unlike your standard 128 kilobits/second [standard for MP3?], ATRAC is fixed at 285.3 kilobits/second. This results in better overall sound quality than your average MP3. In addition, the compression technique is less prone to artifacting (such as that chipmunk-sounding distortion) than MP3s are.
Of course, the biggest advantage MDs have is the fact that re-writeable media is rather inexpensive when compared to the fixed memory of most MP3 players. Blank MDs can be found that store either 60 or 74 minutes of audio for about $5 each. Given that the maximum length of your average audio CD is no more than 74 minutes, you can record and carry around several hours worth of music for relatively little money. This also allows you to change albums on the road, something portable MP3 players today make prohibitively expensive (those memory cards are still the priciest part of the MP3 player). At 7 cm (2.75″) x 6.75 cm (2 21/32″) x 0.5 cm (3/16″), an MD is extremely convenient.
Of course, other benefits of the MD format include its durability and re-recordability. Encased in a hard shell, an MD is not as susceptible to the typical wear and tear of a CD. Also unlike a CD, the MD treats its audio tracks like computer files, as they can be moved around, deleted, inserted, and named without having to re-record the whole MD. A blank MD can be re-recorded thousands of times without losing audio quality too.