Building on the design of the CDP-101, a CD player, Sony worked towards both making better the design of the player, reducing the power and number of parts needed while decreasing the overall size of the player, as well as reducing the cost of the player to a 50 000 - 60 000 yen range in what was called the "CD CD Project", which stood for Compact Disc Cost Down Project. With the function to produce a CD player one-tenth the size of its earliest unit by August 1983, there became potential for a portable player.
The first goal was to create a player that was the equivalent size of four CD cases stacked on top of each other. A piece of wood 13.4 cm across and about 4 cm thick was shown to the staff to illustrate the physical dimensions for which they were going for.
In 1984, Sony was the earliest company ever to introduce the industry's first portable CD player called the D-50. The CD player was released only one year after the introduction of CD's on the market, and since it began to do so well other companies started to release their own portable music players. One of the major problems with the first portable CD players was something called skipping. Skipping consists of the laser inside the CD player temporarily losing its mark on the CD, interrupting playback. In 1993 a solution to this was Electronic skip protection; it is an easy system to reduce disruption of audio from mechanical disturbance of players.
While as of 2010 CDs still are the popular audio medium, portable CD players have seen competition from other forms of portable audio storage. MiniDisc players, flash memory players and audio devices with their own in house storage such as smart phones and the iPod, offer listeners alternatives to portable CD players. The ability to read MP3 CDs has allowed CD players to still compete against these alternatives, although standard CDs are bulkier.