Riddim is the Jamaican Patois pronunciation of the English word "rhythm," but in calypso, dancehall and reggaeton parlance it refers to the instrumental accompaniment to a song. These genres consist of the riddim plus the "voicing" (vocal part) sung by the deejay. The resulting song structure is distinctive in many ways. A given riddim, if popular, may be used in dozens—or even hundreds—of songs, not only in recordings, but also in live performances.
Some classic riddims, such as "Nanny Goat" and "Real Rock", are essentially the accompaniment tracks of the original 1960s reggae songs with those names. Since the 1980s, however, riddims started to be originally composed by producers/beatmakers, who give the riddims original names and, typically, contract artists to voice over them. Thus, for example, "Diwali" is the name not of a song, but of a riddim created by Lenky Marsden, subsequently used as the basis for several songs, such as Sean Paul's "Get Busy" and Bounty Killer's "Sufferer." 
"Riddims are the primary musical building blocks of Jamaican popular songs.... At any given time, ten to fifteen riddims are widely used in dancehall recordings, but only two or three of these are the now ting (i.e., the latest riddims that everyone must record over if they want to get them played in the dance or on radio).... In dancehall performing, those whose timing is right on top of the rhythm are said to be riding di riddim.
Riddims are the instrumental backgrounds of reggae, lovers rock, dub, ragga, dancehall, soca, bouyon, and also grime compositions. Also, rare cases in reggaeton, which itself is largely based on the Dem Bow and Poco riddims by Steely & Clevie from the early 1990s, feature a riddim, such as Ivy Queen and Sasha's "Dat Sexy Body," which uses the Bookshelf riddim produced by Tony Kelly of the K-Licious reggae label.
In other musical contexts, a riddim would be called a groove or beat. In most cases the term riddim is used in reference to the entire background track or rhythm section, but in older roots riddims, riddim is used to reference a certain bass line and drum pattern. Often a melody is associated with the riddim, and occasionally an artist will produce two different songs with the same riddim (e.g. Elephant Man's "Ele Melody" and "Father Elephant" were both produced using the Kopa riddim, produced by Supa Dups).
Some urban contemporary songs may become riddims as well. The instrumental of Ne-Yo's "Miss Independent" became a popular riddim; many dancehall artists have recorded songs using the track. Other songs have inspired riddims as well, such as George Michael’s song “Faith,” which became a riddim of the same name, the Cure's song "Close to Me," which became the Cure riddim, and R. Kelly’s “Snake,” which became the Baghdad riddim. JoJo's "Baby It's You" inspired a hip-hop fusion riddim in the mid-2000s.
African in origin (see clave (rhythm) and bell pattern), riddims can generally be categorized into three types. One of the oldest types of riddim is the classical riddim providing roots reggae, dub, and lovers rock with instrumentals, such as Bam Bam, produced by Sly & Robbie. The second type is the ragga riddim backing raggamuffin and dancehall songs, such as the Juice riddim, produced by Richard "Shams" Browne. The third type is the digital riddim, such as Sleng Teng, produced by King Jammy.
So-called digital riddims refer to riddims created around the time that Jamaican producers incorporated drum machines and synthesizers into reggae-music production (eg. Big Stage Riddim - Produced by Penthouse Records) Nowadays, however, most dancehall and soca riddims are created by electronic instruments, so, in essence, almost all are digital.
Different producers often develop their own versions of the same riddim, such as the Punanny riddim, which has distinct versions crafted by Steely & Clevie and by Ward 21, and different artists often perform on top of the same riddims with different lyrics and different vocal styles, ranging from singing to toasting. As an example, Beenie Man's song "My Wish," Mr. Vegas' song "Go Up," and T.O.K.'s "Man a Bad Man" are all based on the Juice riddim. Many riddims are named after the song that was recorded on that instrumental track for the first time (or, in some cases, the song that becomes the most popular on a given riddim). For example, the Satta Massagana riddim is named after The Abyssinians' original song "Satta Massagana."
Several notable producers include
- Mikey Dread
- Black Chiney
- Bobby "Digital" Dixon
- King Jammy
- Dave Kelly
- King Tubby
- Steven "Lenky" Marsden
- Henry "Junjo" Lawes
- Joe Gibbs
- Donovan Germain
- Steely & Clevie
- Bost & Bim
- No Gimmicks
Since 2000, Greensleeves Records has released a series of compilation albums, based on new and occasionally classic riddims, known as Greensleeves Rhythm Album series. In 2001, VP Records followed suit, releasing the Riddim Driven series. Also following suit was the Jet Star label, with its Riddim Rider series.
- Goodman, Steve (2009). Sonic Warfare: Sound, Affect, and the Ecology of Fear, p.161. ISBN 0-262-01347-9; and Manuel, Peter, and Wayne Marshall (2006). "The Riddim Method: Aesthetics, Practice, and Ownership in Jamaican Dancehall," in Popular Music 25(3), pp. 447-70.
- Stolzoff, Norman C. (2000). Wake the Town and Tell the People: Dancehall Culture in Jamaica, p.126. ISBN 0-8223-2514-4.
- Martin, Billy and Thress, Dan (2006). Riddim: Claves of African Origin, p.4. ISBN 0-9673098-4-0.
- Reggae at DMOZ
- Riddim Database at Jamworld876.net
- Riddimbase - Dancehall & Reggae Riddim Database & Search Engine
- Riddim Database at Frenkieh.com
- Jamaican Riddim Directory