The audio players of today have their roots in the Sony Walkman brand. Aside from radio devices, Sony was the first to introduce a portable music player. The first Walkman devices used magnetic audio cassettes and were kind of bulky at first. Sony first advertised the series in Japan, in 1979. Walkmans were usually powered by two AA batteries and provided good music output provided the source (cassette) was of good quality. Later on came the CD Walkman. It featured the same basic concept: a portable audio player that, instead of audio cassettes, used CDs. The main problem of this device was that, despite being indeed considered "“portable," its size was nowhere near comfortable to use on a daily basis. The best way to carry the device was probably in a backpack. An important problem related to CD players was their limited music storage. A CD could store on average around 20 audio tracks and users would either have to limit themselves to this number or carry with them more CDs. This problem was not solved by the next wave of audio players, but rather the solution gave birth to the next generation of devices. MP3 greatly reduced the amount of data needed to store audio track information. Compared to a CD, an average-sized MP3-encoded song provides an improved compression ration of 1/10. This achievement paved the way of digital music as we know it today. 4 The first Walkman devices were very easy to carry.