In broad terms, the R&B genre, as with any genre of music, is a set of elemental ideas pertaining to culture, instrumentation, melody and groove, that show it to be an expression in its own right. R&B could be basically described as soulful. However, artists of a particular genre have their own unique style or way of expressing these ideas, and contemporary R&B artists incorporate elements or collaborate with artists from different genres such as Hip Hop. And why not? Genres such as pop, urban, R&B, Hip Hop or Funk are all related by that superordinate element... popular!
Alicia Keys is an R&B artist who combines elements from the Soul genre into her style to emphasis the emotion she feels when she performs. The Alicia Keys style would have matured through the process of improvisation, which is commonly used by R&B artists, either whilst performing or during songwriting.