Rhythm and blues, often abbreviated to R&B and RnB, is a genre of popular African-American music that originated in the 1940s. The term was originally used by record companies to describe recordings marketed predominantly to urban African Americans, at a time when "urbane, rocking, jazz based music with a heavy, insistent beat" was becoming more popular.
The term has subsequently had a number of shifts in meaning. In the early 1950s, the term rhythm and blues was frequently applied to blues records. Starting in the mid-1950s, after this style of music contributed to the development of rock and roll, the term "R&B" became used to refer to music styles that developed from and incorporated electric blues, as well as gospel and soul music. By the 1970s, rhythm and blues was used as a blanket term for soul and funk. In the 1980s, a newer style of R&B developed, becoming known as "Contemporary R&B".


Blues is the name given to both a musical form and a music genre that originated in African-American communities of primarily the "Deep South" of the United States around the end of the 19th century from spirituals, work songs, field hollers, shouts and chants, and rhymed simple narrative ballads. The blues form, ubiquitous in jazz, rhythm and blues, and rock and roll is characterized by specific chord progressions, of which the twelve-bar blues chord progression is the most common. The blue notes that, for expressive purposes are sung or played flattened or gradually bent (minor 3rd to major 3rd) in relation to the pitch of the major scale, are also an important part of the sound.
The blues genre is based on the blues form but possesses other characteristics such as specific lyrics, bass lines and instruments. Blues can be subdivided into several subgenres ranging from country to urban blues that were more or less popular during different periods of the 20th century. Best known are the Delta, Piedmont, Jump and Chicago blues styles. World War II marked the transition from acoustic to electric blues and the progressive opening of blues music to a wider audience, especially white listeners. In the 1960s and 1970s, a hybrid form called blues-rock evolved.
The term "the blues" refers to the "blue devils", meaning melancholy and sadness; an early use of the term in this sense is found in George Colman's one-act farce Blue Devils (1798). Though the use of the phrase in African-American music may be older, it has been attested to since 1912, when Hart Wand's "Dallas Blues" became the first copyrighted blues composition. In lyrics the phrase is often used to describe a depressed mood.


Bluegrass music is a form of American roots music, and a sub-genre of country music. Bluegrass was inspired by the music of Appalachia. It has mixed roots in Scottish, Irish and English traditional music, and also it was influenced by the music of African-Americans through incorporation of jazz elements.
Immigrants from England, Wales, Ireland, and Scotland arrived in Appalachia in the 18th (and in some cases 17th) century, and brought with them the musical traditions of these countries. These traditions consisted primarily of English and Scottish ballads— which were essentially unaccompanied narratives— and dance music, such as Irish reels, which were accompanied by a fiddle. Many older Bluegrass songs come directly from the British Isles. Several Appalachian Bluegrass ballads, such as Pretty Saro, Barbara Allen, Cuckoo Bird and House Carpenter, come from England and preserve the English ballad tradition both melodically and lyrically. Others such as The Twa Sisters also come from England, however the lyrics are about Ireland. Some Bluegrass fiddle songs popular in Appalachia, such as "Leather Britches", and “Pretty Polly”, have Scottish roots. The dance tune Cumberland Gap may be derived from the tune that accompanies the Scottish ballad Bonnie George Campbell. Other songs have different names in different places, for instance in England there is an old ballad known as “A Brisk Young Sailor Courted Me”, however exactly the same song in North American Bluegrass is known as "I Wish My Baby Was Born".
In bluegrass, as in some forms of jazz, one or more instruments each takes its turn playing the melody and improvising around it, while the others perform accompaniment; this is especially typified in tunes called breakdowns. This is in contrast to old-time music, in which all instruments play the melody together or one instrument carries the lead throughout while the others provide accompaniment. Breakdowns are often characterized by rapid tempos and unusual instrumental dexterity and sometimes by complex chord changes.


The name Doo-wop is given to a style of vocal-based rhythm and blues music that developed in African American communities in the 1940s and achieved mainstream popularity in the 1950s and early 1960s. It emerged from New York, Philadelphia, Chicago, Baltimore, Newark, Pittsburgh, Cincinnati and areas of greater Los Angeles including El Monte and Compton. Built upon vocal harmony, doo-wop was one of the most mainstream, pop-oriented R&B styles of the time.
As a musical genre, Doo-wop is a type of vocal group harmony with the musical qualities of many vocal parts, nonsense syllables, a simple beat, little or no instrumentation, and simple music and lyrics. It is ensemble singing with single artists appearing with a backing group. Solo billing usually implies that the individual is more prominent in the musical arrangement.