Juju has been the most consistently popular musical style in Nigeria over the last half of the 20th century, with roots in the traditional, mostly drum-based music of the Yoruba (one of Nigeria's largest ethnic groups). In its fully developed form, juju is a dance music played by large ensembles centered around guitar and percussion: several guitarists play interlocking, complex melodies over a thundering wall of rhythm, led by traditional Yoruba talking drums (whose heads can be tightened or loosened while they're being played, in order to change the drum's pitch and more closely mimic human speech patterns). Lyrics are important as well, drawing upon the large storehouse of Yoruba oral tradition -- poetry, proverbs, praise songs -- and the inherently musical qualities of the language, in which the meaning of some words changes with different pitches. Early juju music, which emerged as far back as the 1920s, was essentially an intersection between Yoruba drumming and the socially oriented, string-based palm-wine style, which developed in the drinking houses at the time and influenced highlife music as well. Pioneers like Tunde King and Ojoge Daniel made the first juju recordings during the early '30, but while they achieved a measure of popularity, juju didn't really become a sensation until after World War II, with the advent of electric amplification. Tunde Nightingale was the first real juju star, and during the mid-'50s, he was eclipsed by the legendary I.K. Dairo, who greatly expanded the ensemble (from four musicians to around ten) and became the first juju artist to feature talking drums, electric guitars, and accordion -- essentially shaping the sound of the music into its most widely known form. Chief Commander Ebenezer Obey and King Sunny Ade both began performing around the mid-'60s, and the rivalry that developed between the two during the '70s became a period of intense creative fertility for juju music. Releasing several albums per year, each constantly attempted to outdo the other by expanding their bands, adding new instruments (including keyboards and Hawaiian steel guitars), and increasing the lengths of their songs (each new innovation was dubbed a different "system," spawning hundreds of imitators around Yoruba territory). At the dawn of the '80s, both Obey and Ade brought their music to the international stage, the former with his 1980 album Current Affairs, and the latter by signing to Island for 1982's Juju Music. In contrast to the more conservative Obey, Island hyped Ade as the inheritor of Bob Marley's populist mantle, but when Ade's follow-ups Synchro System and Aura failed to perform up to commercial expectations, he was dropped from the label. Although Ade and Obey continued to command sizable audiences, the mid-'80s brought a general decline in juju's fortunes. Young Nigerians had begun listening to juju-influenced pop music, and the more percussion-oriented fuji style had begun to capture a share of the market as well. Both Obey and Ade continued to record into the '90s, although on a smaller scale and with less regularity (partly due to an increasingly strict governmental regime).