The MiniDisc came out quite a while ago, in the early 1990s, and was quite successful in Japan and Hong Kong. It was smaller than a compact disc, was randomly accessed (so one could access a particular track instantly), ideal for personal players. For a time the format showed a lot of promise. It failed in North America for several reasons:

1. It was proprietary. While Sony avoided its Betamax mistake and licensed the system to competitors, it charged heavy fees. The players were initially very expensive and never came down to a level comparable to cassette or CD players.

2.  North Americans and Europeans are generally not avid early adopters of new formats. It actually took CD's several years to catch on here in the U.S., despite the CD's obvious superiority to vinyl (unless one had very expensive home audio equipment)

3. Minidiscs were hobbled by the Serial Copy Management System. One could copy to MD once, but could not burn the copy to another medium. Minidiscs got a lot of negative press because of it.

4. The average consumer didn't care as much about the increase in quality, especially when he'd have to pay a premium for that quality. A cassette played through a Walkman is going to sound almost as good as a high quality Minidisc Walkman to the average Joe.

5. By the time Minidisc equipment came down in price, CD recorders and blank CD media were becoming affordable to the average consumer, opening the way for the MP3 format and personal music players such as the iPod.

6. MD was only halfheartedly supported by the recording industry. Prerecorded Minidiscs were few and far between in North America.

If Minidiscs were to succeed, it would have been as a replacement for the analog cassette in the early 1990s. Sony squandered that opportunity by pricing it far above cassette technology. It survived as long as it did by its technical merits until the rise of affordable CD recording technology and digital MP3 (or other format) audio.