Well, ever since Bill Wyman decided to pull the frets from his self made bass to improve the way it played, people have been going the fretless way and its typical "Mwaaaah" sound is a fixture of contemporary music since. But let's talk about the instances where people pushed out the boat on what a fretless bass can do. First up and did you really expect anybody else? Legend says that Jaco did this as a showcase of "THIS is what I can do!" it also opened people's eyes to what a fretless bass could do. One guy who's eyes were opened was Les Claypool, who decided to combine a fretless bass with Tony Levin's Chapman stick playing on Primus' "Jerry was a race car driver." On the recording itself Les used a Tune six string which he pulled the frets from himself but as this clip shows, used a custom Carl Thompson six string to perform it live.