Listening to an entire album of pop songs by former Fairport Convention guitarist Richard Thompson is a lot like dining with Einstein a profound but unsettling experience. For instance, on Rumor & Sigh such songs as the witty and wry ''Read About Love,'' ''Backlash Love Affair,'' and ''Feel So Good,'' though unbelievably catchy, all have a strong undercurrent of irony, while a few others ''Mother Knows Best'' and the cabaret number ''Psycho Street'' are silly on the surface and downright bitter underneath. On the lovely ''1952 Vincent Black Lightning,'' Thompson acknowledges his roots as one of Britain's premier folk-rock revivalists with a shimmering play of acoustic folk guitar, while on ''God Loves a Drunk'' and ''Why Must I Plead'' he solidifies his reputation as a songwriter who is unafraid to tackle sheer sadness as his subject matter. In short, Rumor & Sigh is musically diverse, emotionally moving, lyrically intelligent, and intimidatingly grown-up four things that are each rare enough in rock & roll as to be positively disturbing when found in a single package. A

