Michael Hedges is the best thing to happen to the acoustic guitar since Leo Kottke. Hedges brings to bear a new array of techniques -- hammer-ons, pull-offs, finger-slides, bell-tones and many altered tunings -- and then makes one forget they are techniques. He manages to find new Records sounds on this thoroughly explored instrument and then bends these sounds to the absorbing moods and personal lyricism of his compositions.

Hedges' second album, "Aerial Boundaries" (Windham Hill WH-1032), is even more assured and accessible than his dazzling 1981 debut, "Breakfast in the Field." It doesn't sound as reserved this time, as if he's willing to reach out to the listening audience more. He does this, though, without the indulgent, digressive romanticism that leads some Windham Hill artists all over the lot in the name of spontaneity. Hedges knows where he's going, and every note he plays counts.

Raised in Oklahoma, trained in Baltimore and now based in San Francisco, Hedges has been both a classical composition student and a folk-pop bar singer. The reassuring, cyclical progressions of folk music are present, though often in the strangest of keys. Over and between these vernacular phrasings, Hedges slips in his stark melodic whines and brilliant effects. Thus the listener gets the familiar grounding of folk music as well as the stimulation of serious composition. Just as important, Hedges' muscular, rhythmic accents keep his tunes sharp and attentive.

The album's title tune opens with a little rhythmic figure that is soon overwhelmed by a folk progression that unwinds section by section. In turn, this easy momentum is interrupted by echoing pull-offs and brusque chording. Finally, highly melodic phrases flash through all this activity. Unless one has seen Hedges live, it's hard to believe that all these sounds come from one guitar recorded live.

Hedges nods toward several musicians he admires. "Bensusan" pays tribute to the French acoustic guitarist Pierre Bensusan -- a quiet piece that stays exceptionally fluid over tricky runs and changes. With its circular figures and end-line accents, "Ragamuffin" recalls the baroque-folk guitar of Bert Jansch and Alex de Grassi. "Spare Change" is a collage of guitar sounds altered and re-edited in a Baltimore studio as a tribute to the pulsing minimalism of Steve Reich. All these pieces, though, have the textures and accents that are Hedges' alone.

Hedges includes one outside composition, Neil Young's "After the Gold Rush," which becomes an instrumental showcase for the much underrated fretless bassist Michael Manring, who combines Young's lyricism with Jaco Pastorius' jazz techniques. Manring joins Hedges and the latter's wife, flutist Mindy Rosenfeld, on the seven-minute trio piece, "Me'nage a Trois." Otherwise the album consists of solo guitar. The two best pieces, "Rickover's Dream" and "The Magic Farmer," have the kind of luscious melodies that would beg for a singer if Hedges' guitar weren't so expressive by itself.

Micheal O'Domhnaill was the guitarist in Ireland's progressive folk group, the Bothy Band, from 1974 to 1978. During those years and ever since in his duets with fellow Bothy alumnus Kevin Burke, O'Domhnaill has pushed against the limits of traditional Irish folk music in search of a Celtic form of folk-jazz. He has found an appropriate vehicle for that quest in his duet album with fiddler Billy Oskay, "Nightnoise" (Windham Hill WH-1031).

Though the influence of Irish folk music is unmistakable throughout this album, the duo's original compositions are more open-ended in rhythm, structure and progressions. O'Domhnaill provides most of the album's gravity as his stop-and-go acoustic guitar figures patiently explore a theme. Oskay's violin or viola will come sweeping across the top with a florid extension of O'Domhnaill's groundwork.

The album's highlight is O'Domhnaill's seven-minute composition, "Bridges," built around an understated melodic figure that gives the piece a nocturnal, meditative quality. The piece's admirable leanness allows the duo to keep shifting the motif ever so subtly to keep it fascinating. O'Domhnaill's other compositions, notably the whistle-enlivened "American Lass," share this sparse beauty. Oskay's compositions tend to get overly cluttered, with too many overdubs, especially on the two side-openers. This album could have been more if it had been less.

Three of Europe's top acoustic jazz pickers -- fiddler DiDier Lockwood and guitarists Philip Catherine and Christian Escoude -- have joined forces in Paris for the album "Trio" (Gramavision GR 8403). Obviously made in the spirit of Django Reinhardt and Stephane Grappelli, the nine tunes swing crisply and lyrically. Although the three players mix electric instruments with the acoustic, the effects are restrained and retain a gypsy feel.