Music is an international language - how's that for finding? Nashville singer/songwriter and virtuoso bluegrass mandolin-player Tim O'Brien has initiated "The Crossing" project to explore the premise with relation to acoustic folk.

"The Crossing" is an album and a band with a shifting line-up of major Irish, American, Scottish and Irish traditional performers who work together to explore the links between their different inheritances.

I wonder, however, whether the exploration goes far enough. O'Brien, who I have seen performing in Glasgow, Donegal and Dublin, seems to be making a link between Irish music and the American acoustic tradition in order to understand himself as a musician and a person. This comes across - sentimentally to an Irish listener - in songs like The Wild Geese, in which he sings of "The voice in the heart that calls for home."

No one would argue against the link; no-one could, listening to O'Brien perform One Evening For Pleasure with whining bluegrass fiddle and dizzying mandolin. There is, however, a host of other links between different brands of contemporary acoustic music and this was underlined when the band played The Beatles' Norwegian Wood on Sunday night. Now that's a common inheritance.

When you hear the magnificent Yorkshire folk singer Kate Rusby, harmonising on Tim O'Brien's bluegrass Down on the Banks Below, it makes you less certain of the specific Irish-American influence, more certain of the common ground between all folk musics, and very, very certain that we're all children of the 1960s folk revival.

Kate Rusby, as pretty as the Christmas tree fairy, and with a Yorkshire toffee of a rich, strong, melting voice, seems to have an audience here avid to hear more of her - there was a queue of autograph-hunters after the gig.

Within the format of this collaborative gig, we only heard two of her stunning songs, the gorgeous Wild Goose and All God's Angels, a harrowing tale of a girl left pregnant and abandoned: "I'll run to the fields/ And it's there I'll die/There God's Angels will around me fly/There they'll care for my child and I."

On Rusby's Sleepless, O'Brien sings the part of her lover, and this shows another level of the links in contemporary acoustic music in the jet travel age; the musicians not only play each other, they know each other.

The embarrassment of riches on stage included Mairtin O'Connor on the box, Kentucky/ Nashville singer/guitarist Daryl Scott and John Mc Cusker's dramatic Scottish fiddle, pairing dazzlingly with O'Brien's mandolin to dance from Scottish to baroque to Balkan influences.

In the end, however, the collision of styles in the gig did not make up for the dulling of the effect of each individual master.