Portishead (2 Lp's)Portishead: Beth Gibbons (vocals); Adrian Utley (guitar, piano, Fender Rhodes piano, Moog synthesizer, bass); Geoff Barrow (drums). Additional personnel includes: John Baggot (samples); Sean Atkins (background vocals). Like Soul II Soul a few years before them, Portishead spearheaded a revolution in both pop and dance music by introducing a distinctive new groove. Portishead was at the vanguard of the '90s trip hop onslaught, and after a three year