用英文介绍一下蓝调音乐

[我看到好多图像采集卡介绍中都提到了二次开发包SDK这个是]其实很简单. SDK 就是 Software Development Kit 的缩写，中文意思就是“软件开发工具包”。这是一个覆盖面相当广泛的名词，可以这么说：辅助开发某一类软件的相关文档、范例和工...+阅读

Rhythm and Blues was and still is a term used for a number of post-war American popular music forms. The term is credited to Jerry Wexler when he was editing the charts in Billboard magazine (1947). The term was used in the chart listings from 1949 onwards and the charts in question encompassed a number of contemporary forms that emerged around that time. R&B clearly has its origins in the secular folk music of the American black musician - the Blues. For me, the Blues is essentially about emotional expression and is predominantly a vocal medium - although there are many examples of blues instrumentals to refute this assertion, it is the singer who expresses the feelings of the blues; and there are a number of vocal techniques which are used to create the desired effects. There are of course a range of blues intrumentations which accompany the central vocal performance (the bending of guitar strings, the classic bottleneck of so many of the great blues guitarists, the harmonica imitating the idioms of the human voice etc. etc.) and which clearly help to create the unique blues performance. Although much has been written on the blues, the origins of the music are not particularly well documented. It is clearly influenced by the work songs of the deep South, ragtime, church music, minstrel shows and folk, even some forms of white popular music. The earliest and most frequently cited references to the form are to be found in the early 1900s and one of the early musical reference points is the W.C. Handy composition 'Memphis Blues'.Rural blues developed mainly in the three key regions of Georgia, Texas and Mississippi. Excellent examples of the Georgia style include Blind Willie McTell and Blind Boy Fuller, highly melodic and less intense than the Mississippi stylists such as Charley Patton, Robert Johnson and Johnny Shines. Interestingly however, perhaps the first real blues recordings were made in the 1920s by the women of the blues, artists such as Ma Rainey, Ida Cox and the wonderful Bessie Smith. At this stage the performances were still largely based on their stage backgrounds, backed by the leading jazz players of the day.Muddy Waters One of the critical external factors which moved the blues form forward was the economic migration from the American South to the cities of the North by millions of black southern workers. The blues went with them, adapting to a more sophisticated urban environment. The themes of blues songs understandably became more urban, the solo bluesman was joined by a number of other musicians and the blues combo was born. The piano, harmonica, bass and drums and, most importantly of all, the electric guitar became the cornerstone of a sound of increasing rhythmic intensity.Some of the major urban conurbations included Atlanta, Memphis and St. Louis but there are critical milestones to be found in any number of places. John Lee Hooker found a home in Detroit, the great T-Bone Walker established a following on the West Coast and Chicago exerted an influence of real significance - Sonny Boy Williamson, Muddy Waters, Little Walter, Howlin' Wolf, Elmore James and Otis Spann were all based there.The Blues has influenced just about everything musically which subsequently developed. Not least of which was the emergence of what came to be known as Rhythm and Blues