Tubby's work at Duke Reid's studio, where he was disc-cutter, led him to discover dub. He found that by dropping out the vocal track and remixing the remaining rhythm tracks he created new 'versions' of much-loved tunes. He began to record a series of special acetate recordings or dub plates for exclusive use on his sound system. The space left by the absent vocal tracks enabled U-Roy to improvise his own jive-talk raps or toasts when the sound system played dances. The effect in the dancehall was immediate and electrifying. In 1969 U-Roy was invited to play for Dodd's Down Beat sound system, playing the number 2 set; the number 1 set had King Stitt as DJ.
