Rap is a vocal style that resembles a cross between singing and chanting. Rapping relies heavily on the ability to rhyme distinct words. These words are called rap lines or rhymes. Music is used to set the tone for the dance party or night out with friends. Singing is using your voice to express yourself emotionally or lyrically through song. This form of art is very popular in rock, pop, and alternative music genres. Rappers use their voice to create a rhyming language all its own. Much like poets who use words to create poems, rappers use phrases known as bars to write songs. A bar is a sequence of four measures of music (usually beats per minute), followed by a pause of about two seconds, during which the rapper delivers his or her line. The word "bar" comes from the verb "to march," because this type of rhythm feels like it keeps time well for marching down streets or around blocks. In addition to using music, rappers may also use certain words as hooks or catchphrases to get attention from listeners. For example, someone might call out another person's name upon seeing him or her at a party or event, knowing that this will make them come over to find out what's going on.