High Quality Content by WIKIPEDIA articles! A music download is the transferral of a song from an Internet-facing computer or website to a user's local computer. This term encompasses both legal downloads and downloads of copyright material without permission or payment if required. Popular examples of online music stores that sell digital singles and albums include the iTunes Store, Napster, Zune Marketplace, Amazon MP3, TuneTribe, Kazaa and eMusic. Paid downloads are sometimes encoded with Digital Rights Management that restricts making extra copies of the music or playing purchased songs on certain digital audio players. They are almost always compressed using a lossy codec, reducing file size and therefore bandwidth requirements. However, this may cause an apparent loss in quality to a listener when compared to a CD, and cause compatibility issues with certain software and devices. Digital music sales now generate around $2 billion in revenue, with tracks available through 500 online services located in 40 countries, representing around 10 percent of the total global music market.