Recording audio started towards the end of the 19th century with Thomas Edison's phonograph. This was a machine (that consisted of a tinfoil cylinder and a speaker that resembled the megaphone) that he invented and used to make a recording of Mary Had a Little Lamb, the first song recorded. This moment was crucial in the history of recorded sound. Wax, metal and other materials are shaped into cylinders and disks were used for at least 50 years. In 1929 the vinyl records were made and dominated the scene for the next forty years. Amazingly enough magnetic tape was developed at the same time but it only gained popularity in the 1960s. In 1985, the Compact Disc was developed by Sony and Philips and instantly became a huge success and, 13 years later, the portable MP3 player then made its debut. It was a breakthrough that would change everything; we can now store and listen to a massive amount of music, not just a few songs that use up all the memory of the player. So, in order to be able to store much, we must get the file compressed. This is where the codec software enters the stage; it can convert analogue music to a smaller digital file which is then stored in the memory of the MP3 (the air pressure waves that we hear as sounds bear the name of ‘analogue audio' when they are recorded). MP3 files can be constructed at higher or lower bit rates, with higher or lower resulting quality. A mid-range bit rate setting of 128 Kbit/s results in a file of about 1/10th the size of the file created from the original source. When we listen to our music, the software that has been embedded in the player reads the file which then decompresses it, converts it to analogue, amplifies the signal and transfers it to the headphones. This, in a nutshell, is how it works. As for the hardware, there is a laser device that reads the CD's, just as the stylus works for the records and a magnetic head for cassette tapes. The idea no longer looks puzzling now that several types of MP3 players have been created and the future of the system is likely to store even more revolutionary devices of the kind. We will certainly see an increase in a wide range of products but, for the time being, there are only three types of MP3 players available. The smallest, cheapest and probably the most reliable of all are the Flash Players. Their batteries are long lasting due to the fact that they have no moving parts. The capacity of these players has already reached 4GB and will surely increase in the near future. The newest models are about the size of a credit card. Hard Drive Players can have a memory of 80GB so they can hold thousands of tunes, photos and videos. All this on a device that is about the size of a deck of cards. Last but not least, the latest generation of portable CD-players, the CD MP3 players, employ MP3, ATRAC and WMA formats; some of them can even burn CDs, and will hold 10 to 45 hours of music per disc. There are also Minidisk models, a little more expensive than the standard ones