The Guilfoyle brothers, perhaps the tightest and most "out-there" jazz rhythm section in the country, trade phrases easily in conversation. But mostly it falls to 39-year-old Ronan (bassist, composer and father-of-two) to do the mouth-work; with drummer/ percussionist (and father-to-be) Conor, two years his junior and nervier (the night we met, he was wiring himself up for a midnight gig), filling in information in staccato bursts.

While both have independent careers, their symbiosis has provided the bedrock for a range of impressive achievements. This year between them, they have released three albums with the Arts Council-supported Improvised Music Company label - as well as Ronan's Music For Clarinet And String Trio recorded by the Hibernia String Trio on CD.

On IMC, there's Conor's upbeat salsa band, Saoco, blending Irish jazz musicians with Cuban vocalists - a culmination of a long affair with Latin music.

Another diverse outfit is Khanda, a bizarre collision of Irish traditional music with Ronan's compositions; backed by Arab/Latin beats (Conor), and Indian drumming and melody (Ramesh Shotham). Ronan says: "Southern Indian music is based on long melodic phrases - which, to my ear, has a lot in common with Irish trad."

Trad purists may have their ears bent out of shape by Khanda's jazz overtones, but Ronan insists there is a logic: "Rhythmically, Irish music is based on triplets. Even a reel, though allegedly four/ four, is decorated in triplets. It's the same with jazz, the only difference being syncopation. But it's fundamentally the West African root of three against two."

But what about the chords? "Sure, they're different, but they're within the same modal family as the melody. They just create an otherworldly atmosphere." He cites a session with Paddy Glackin and Liam Og O Flionn over the disorienting Guilfoyle rhythm section. "Those were Protestant chords," growled Glackin ironically afterwards, but, says Ronan: "I think they liked it." Conor: "Yeah, but they never hired us."

Yet another band, Devsirme, is more jazz-focused on Ronan's complex polyrhythmic compositions with, as usual, breaks of freeform improvisation - a recording which, three weeks ago, won him the prestigious Julius Hemphill award in Boston.

Again, Conor is pushing the pace on drums, behind saxophonists Brendan Doyle and Michael Buckley, and trombonist Karl Ronan (now touring with Oasis).

"I'm going for an extended compositional style, which is commoner in, say, 16-piece orchestras. Even with the drums, I'm very specific, whereas normally, a drummer just gets a sheet with the dramatic accents."

Conor: "A lot of people don't know how to write for drums, but we've worked so long together, it's very much a two-way thing."

But jazz composition also has a strong tradition, going back to Duke Ellington, Thelonius Monk, Charles Mingus, George Russell - they all knew who they were writing for, so in an improvised section, they knew pretty much how it was going to turn out."

Another aspect of Ronan's career since 1993 has been contemporary-classical compositions, some for the RTE Concert Orchestra. So far he has notched up a guitar concerto, a 30-minute concerto for full orchestra, a violin sonata, a wind quintet, a sax quartet and a major concerto for the virtuoso classic accordionist Dermot Dunne. He's now most of the way through a violin concerto, again for RTECO.

"When that's over, I intend to stop writing for a while and get back to practising. I'm so busy writing, which is not a bad complaint, but it can be dangerous if you're an instrumentalist."

The second and third of eight children, they grew up in Crosthwaite Park in Dun Laoghaire, Co Dublin, where they were tuned in to their late father's very specific tastes in music: Mingus, Coltrane, Miles Davis; and classical music from Bartok and Shostakovich back to Ravel and Debussy.

Ronan: "It was a tremendous osmotic education. He'd quiz us: `Is that an oboe or a horn?' Or put words to instrumental jazz and blues tunes, and get us to sing them." It certainly had an effect.

Ronan: "I remember walking to the shop as a kid, making up tunes."

Conor: "I used to tap away on cushions, destroying my mother's knitting needles, or the metal rack out of the fridge." They laugh, coughing up teenage influences: Slade and Deep Purple, on to King Crimson and Cream, and into Matching Mole, Back Door, Gentle Giant.

The reconversion to jazz came with the Mahavishnu Orchestra's Birds Of Fire and, under the influence of Herbie Hancock and Billy Cobham, they bought bass and drums.

However, after their father died in 1975, there was pressure to nail down a day job. Conor whiled away some years as a store manager, while Ronan worked in a delicatessen for a decade. But they kept up the music.

By chance, in the tiny jazz record shop in Gaiety Green, Ronan met Richie Buckley, whose father Dick was a well-known jazz player.

"Obviously Dick was badly stuck for a bass player, but I got this phone call. I was very nervous going in, and they asked me did I know any Charlie Parker, and what keys I could play it in, and I said, `any key you like', because once I found the first note, I was fine. But they took this as a sign of incredible advancement."

In fact, he couldn't even read music - yet within six weeks, he was playing with Louis Stewart.

Conor emerged through lessons with John Wadham. "His teaching methods were basically put on records and get you to play to it; but he had this incredible selection."

Yet despite the prodigy status of earlier years, Ronan still smarts at the way his material was received by some of the older heads. "In the jazz world, there's a conservative element which saw me as intellectual and arrogant, and by straying outside bebop, I was somehow denigrating the music, or couldn't play it properly."

Conor felt it as well: "I'm completely a jazz drummer, even though I've studied Indian tabula, Latin timbales, different drum sets. But the problem to some people is that I'm not a 1950s jazz drummer from New York. The trio are always working in metres, sevens and nines, while an awful lot of jazz is four/four. So what comes out is a product of all those influences."

Another Guilfoyle interest is teaching jazz improvisation in Newpark Music Centre, Blackrock, Co Dublin, in the first full-time jazz diploma course in the country (recognised by the International Association of Schools of Jazz) which Ronan co-founded with Simon Taylor and American sax player Michael Fuller.

Certainly his own and Conor's scholarships to the Banff Centre in Canada stood to them. There, at different times, they learnt from heavyweights John Abercrombie, Dave Liebman, Larry Koryell and many more. But Ronan brings it back to his father.

"I'm convinced the reason both of us play is because of my father. I still wonder what made him such a maniac for music, when he didn't play an instrument. Maybe some people enjoy music on a purer level. If you're a musician, it's hard to forget the nuts and bolts, but maybe all you really need to know is whether it reaches you or not."

Fact File

The brothers: As well as both being increasingly influential jazz teachers, brothers Ronan (bass) and Conor (percussion) Guilfoyle are an eclectic rhythm section. Apart from their trio with brother-in-law, guitarist Mike Nielsen, the pair come together with other musicians in a number of formats, most recently, Khanda, which has just released its debut CD.

Since 1993, Ronan has also composed widely for classical ensembles, and his 30-minute concerto for the full RTE Concert Orchestra will be broadcast soon.

Apart from leading a number of jazz and fusion outfits, Conor has forged a racy drum style by blending Latin, Arabic, Indian and jazz percussion, and now leads the Cuban-Irish salsa band, Saoco, whose first album, Descarga, has also just been released.