Rapping, also referred to as MCing or emceeing, is a vocal style in which the performer speaks rhythmically and in rhyme, generally to a beat, recently, however, a difference has developed between "rapping" and "MCing". "MCing" has been used to describe those artists who possess and exercise superior lyrical ability and prowess. Beats are traditionally generated from portions of other songs by a DJ, or sampled from portions of other songs by a producer, though synthesizers, drum machines, and live bands are also used, especially in newer music. Rappers may perform poetry which they have written ahead of time, or improvise rhymes on the spot with or without a beat. Though rap is usually an integral component of hip hop music, DJs sometimes perform and record alone, and many instrumental acts are also defined as hip hop. Hip hop arose in New York City when DJs began isolating the percussion break from funk, or rock songs for audiences to dance to
recognition, selling over one million albums in the UK and over ten million worldwide. Placebo are best known for hit songs such as "Nancy Boy", "Pure Morning", "Every You Every Me", "Infra-Red", a cover of Kate Bush's "Running Up That Hill", and "For What It's Worth". Their style has varied greatly. The band's first album featured a raw sound and a fairly minimalistic instrumental lineup, but proceeding albums have had a slower, more melancholic tone and they started experimenting with synthesizers and other, less traditional, forms of sound production (particularly after Black Market Music).The band have gained some measure of notoriety for the sexualities of its members (Olsdal is gay and Molko is bisexual) as well as for their excessive lifestyles and Molko's androgynous image, which are often referred to in their songs. In 1998, Placebo switched to the major label Virgin Records, and issued their album Without You I'm Nothing in November
lator or optocoupler) houses an LED and a phototransistor in a package like an IC. The optical isolator is sealed—there is no way to break the light path. The optical isolator is not used to detect mechanical motion, but to provide electrical isolation between two electrical circuits. A common use for optical isolators is to isolate a high-voltage circuit from the microprocessor that con- trols it. MIDI (Musical Instrument Digital Interface) uses optical isolation to connect synthesizers, computers, and other electronic musical instruments. In this application, the use of optical isolators prevents problems caused by different ground potentials. Sensors 67 Figure 3.12 Optoisolator. Figure 3.12 shows how an optoisolator can be used to pass signals from one system to another. The ground and power connections for the system may be completely separate. Even in a single system where the grounds
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