Music is steadily developing. Inside the last 100 years music has changed substantially - because of the rise and fall associated with the Beatles, age of techno musical, actually the little reign of grunge rock in the 90s - and proceeds on to improve with each passing day. Among the many more recent trends in musical is DJ - or dance - music. A DJ, sometimes known as a disk jockey, is - by definition - someone who selected documented singing and plays it back for a readers. Unfortunately, there are lots of different sub-classes of DJ. They are: