Encyclopedia of Computer Science and Technology

326 music and video distribution, onlinehave also been based on applying mathematical structures(such as fractals) and the concepts being discovered bycomputer scientists, including adaptive structures such asneural nets and genetic algorithms.Like most avant-garde music, computer music compositionremained largely unknown to most people. However,the technology of music synthesis was to become democraticallyavailable to everyday musicians as well. As thepersonal computer began to bring increasingly powerfulmicroprocessors to consumers, it became practicable toin effect add a music synthesizer to the PC. The musicalinstrument digital interface, MIDI, provides a protocol forconnecting traditional musical instruments such as pianosand guitars to a personal computer. MIDI specifies the pitch,volume, attack (how a note increases to maximum volume),and decay (how it dies away). The musician then uses theinstrument as an input device, with the notes played beingrecorded as MIDI data. Different tracks can then be edited(such as to transpose to a different key), and combinedin various ways to create complete compositions. BecauseMIDI stores instructions, not actual digitized sound, it is aquite compact way to store music. MIDI brought the synthesizerwithin reach of just about any serious musician—andmany amateurs.PC sound cards can play sound in two ways. Wave TableSynthesis uses a table of stored digital samples of notesplayed by various instruments, and algorithmically manipulatesthem to reproduce the MIDI-encoded music. FM Synthesisattempts to create waves that replicate the intendedsounds, based on a model of what happens in a given instrument.It is less faithful to the original sound, since it doesnot capture the detailed “texture” of a digital sample.Today’s PCs have sound cards that can handle bothplayback of audio CDs and rendering of digitized and synthesizedsounds. The cards have the capacity to supportmany simultaneous voices (polyphony) as well as renderingspeech faithfully. While early PCs tended to have onlytiny internal speakers, most PCs today come with speakers(often including subwoofers and even multiple speakers for“surround sound”) comparable to midrange home stereosystems.Of course great hardware would not be very useful withoutsoftware that can help even beginning composers turntheir ideas into sound. One example is GarageBand for theMacintosh, which makes it easy to make compositions fromsampled and sequenced loops together with music playedusing sampled and synthesized instrument sounds and aMIDI keyboard. (Sony ACID Pro offers similar features forMicrosoft Windows users.)Further ReadingBurns, Kristine H. “History of Electronic and Computer MusicIncluding Automatic Instruments and Composition Machines.”Available online. URL: http://eamusic.dartmouth.edu/~wowem/electronmedia/music/eamhistory.html. Accessed August 15,2007.Freebyte Music Zone. Available online. URL: http://www.freebyte.com/music/. Accessed August 15, 2007.Manning, Peter. Electronic and Computer Music. New York: OxfordUniversity Press, 2004.Nelson, Mark. Getting Started in Computer Music. Boston: ThomsonCourse Technology, 2005.White, Paul. Basic MIDI. London: Sanctuary, 2004.Williams, Ryan. Windows XP Digital Music for Dummies. Hoboken,N.J.: Wiley, 2004.music and video distribution, onlineSince most audio and much video is now recorded in digitalformat, the Internet and media-player software for a varietyof platforms are an attractive way to sell or otherwise distributethe products of musicians and moviemakers.For a time, online file swapping (see file-sharing andp2p networks), particularly Napster, seemed to be massivelyeroding the market for online commercial musicsales. Legal action against file-sharing services and (startingin 2003) their users has curtailed this erosion somewhat,with a considerable number of former file-sharers switchingto buying paid downloads. As a result, several major onlinemusic stores have become successful. The most commonmodel sells songs for about a dollar each—sometimes morefor higher quality audio or files that do not have copy protection(see digital rights management).Apple’s iTunes Music store debuted in 2003 and soonbecame the market leader. The combination of the iTunesstore, the iTunes media player software (available for bothMacintosh and PC), and the very popular iPod (see musicand video players, digital) has been very successful. Asof 2007 iTunes still had the largest selection of music available(about 6 million songs), and had sold more than 3billion songs. The service also sells videos (television episodes,music videos, short films, and feature-length movies)at varying prices.Rhapsody, a service that predates iTunes, offers a subscriptionmodel: The user has unlimited streaming accessto the music as long as the monthly fee is paid as well as thepay-per-track option.Alternative ModelsThere are also alternatives to the big, label-controlledmusic services. A number of services now bring togetherindependent musicians and their audience. There are alsosome innovative pricing models. Arnie Street, for example,starts out with uploaded music being available free, butthen gradually raises the price (up to 98 cents) as morepeople download it. The service also offers user participation(keyword tagging by users) and social-networking features.Another service, eListeningPost, lets musicians postmusic that people can download as a preview (playable alimited number of times) or buy using PayPal. The servicealso helps musicians build their fan base by collecting e-mail addresses.VideoVideo-sharing sites are very popular (see YouTube). TVnetworks are now providing selected episodes of popularshows online for free, hoping to entice more regularviewers. However, only 7 percent of users surveyed by thePew Internet & American Life Project in 2007 said they