ON RECORD, ON STAGE LENNY BREAU - "Five O'Clock Bells" (Adelphi AD 5006). DANNY GATTON - "Redneck Jazz" (NRG Nr9646). UNICORN TIMES BENEFIT - The Cellar Door, April 25, 8 & 11 p.m. $8, reserved seats.

The names are not familiar, but Danny Gatton and Lenny Breau may be two of the best guitarists of their generation.

Neither has had much commercial success: Gatton's had two albums on small area labels and still plays in local bars, and Breau, after making two poor-selling records for RCA in the late '60s, drifted from the scene. Both men, though, have earned the respect of their guitar-playing contemporaries.

Gatton's ability to shift from jazz improvisations in odd signatures to blazing bluegrass breakdowns to crying blues slide solos is striking. And Breau's ability to play bass lines, rhythm chords and single-note solos all at once is impressive.

BREAU'S "Five O'Clock Bells," his first record after 10 years of inactivity, is the best album of guitar duets ever recorded by one person.

Without the benefit of overdubbing, the guitarist plays walking bass lines with his thumb, brushes chords with his outer fingers and picks out lead notes at the same time. He is the only musician on the record, and despite his background in Nashville, the emphasis is clearly on jazz. Breau's ability to accompany himself gives his playing a sense of interior dialogue that makes other jazz guitar sound incomplete by comparison.

And the dialogue is fascinating. On McCoy Tyner's "Visions," the theme is echoed by haunting, fading arpeggios.Then new flights of improvised notes rise from the dying chords. On the old standard, "Days of Wine and Roses," the graceful lead lines inevitably fall back into the gravity of his tugging bass line. "Little Blues" opens with a hard-swinging bass line that is finally chased down by a spright melody. The record's only misstep is Breau's weak vocal on the title tune.

DANNY GATTONS'S latest album, "Redneck Jazz," is a mixed blessing. It's a fine sampler of Gatton's guitar arsenal. His full-speed-ahead bluegrass picking is displayed on "Truck Driving Romance"; his knack for swing on the title cut; his imaginative but hard rocking on several other songs. But too many tunes are undermined by an indifferent rhythm section and derivative Southern boogie vocals.

Gatton's best moments come on the three instrumentals: "Sax Fifth Avenue" shows how impressive he can be technically, even at slow tempos; "Comin' Home Baby" is a dazzling eight-minute jazz duet of cascading notes between Gatton and pianist Dick Hemtze; and "Rock Candy," recorded during Gatton's first encounter with Buddy Emmons (Guitar Player magazine's pedal steel guitarist of the year) turned into a fret race that stimulated Emmons so much that he has now joined Gatton's new band.

Gatton and Breau will appear at the Cellar Door Wednesday in a "showdown" councert to benefit Unicorn Times, the monthly arts tabloid. Proceeds will go to the paper's unpaid writers. CAPTION: Picture, DANNY GATTON, HALF OF WEDNESDAY'S BENEFIT BILL.By Chas. de Limur.