Premise: A fretless guitar is a guitar without frets , such that fingering its strings at particular positions on the string is done by pressing the string against its fingerboard . Jeff Ament . Along with Stone Gossard , Mike McCready , and Eddie Vedder , he is one of the band 's founding members , and is also known for his work prior to Pearl Jam with the 1980s Seattle-based grunge rock bands Green River and Mother Love Bone , and is particularly notable for his work with the fretless bass , upright bass , and twelve-string bass guitar .
Hypothesis: Jeff Ament is an American who plays rock on the bass guitar.
Label: ENTAILMENT