Dub is characterized as a "version" of an existing song, typically emphasizing the drums and bass for a sound popular in local Sound Systems. The instrumental tracks are typically drenched in sound processing effects, with most of the lead instruments and vocals dropping in and out of the mix. The music sometimes features processed sound effects and other noises, such as animal sounds, babies crying, and producers shouting instructions at the musicians.
These versions are mostly instrumental, sometimes including snippets of the original vocal version. Often these tracks are used for "Toasters" rapping heavily-rhymed and alliterative lyrics. These are called "DeeJay Versions". As opposed to hip hop terminology, in reggae music the man with the microphone is called the "DJ", while the person operating the turntables is the "Selector".
A major reason for producing multiple versions was economic: A record producer could use a recording he owned to produce numerous versions from a single studio session. Version was also an opportunity for a producer or remix engineer to experiment and vent their more creative side. The version was typically the B-side of a single, with the A-side dedicated to making a popular hit, and B-side for experimenting and providing something for DJ's.
See in particular the works of Lee Perry, King Tubby (Osbourne Ruddock), Errol Thompson, Prince Jammy, Keith Hudson and Augustus Pablo for the very best in dub music in the 1970s.
In the '80s Britain became a new center for dub production with Mad Professor and Jah Shaka being the most famous, while Scientist became the heavyweight champion of Jamaican dub.
In the 1990s and beyond dub has been influenced by and in turn influenced techno, dance music, ambient music, and hip hop, with many dub tracks produced by non traditional musicians from these other genres. Musicians such as The Clash, PiL, The Orb, Pole, Underworld and others demonstrate clear dub influences in their respective genres, and their innovations have in turn influenced the mainstream of the dub genre. Traditional dub has, however, survived (see Aba Shanti-I, for example) and some of the originators like Lee Perry and Mad Professor continue to produce new material.