Edinburgh Napier University

  Dempster's 2005 quartet, his fourth, is entitled The Cold Dancer, and is immediately compelling through its savage attacks with scrunchy chords, searing melodic lines and seething textures. It's a bit Bartok-y in this respect, with huge expressive surges, all breathtakingly complemented by music of a beautiful, hymn-like simplicity.

Clapperton's 1990 quartet, The Great Divorce, is an extraordinary piece played entirely on muted strings and with the ethos of an intimate, murmured conversation overheard from afar. It has such emotional coherence that, even when the music speeds up and assumes a dance-like step, it loses none of that intimacy. And there is a devastation coup de theatre towards the end when, in the course of a heart-rending cello melody, a skittish little jig flits impertinently across the horizon.

Judith Weir's 1990 String Quartet is the best-known of the pieces. Drawn from a song, the music is lyrical throughout, with organic streams of melody. It is Scottish to its core and the roots of its soul. The glorious finale is a dazzler, with a Sibelian intensity to its racing and scurrying, shot through with the lilt and step of a Scottish folk dance.

Arguably, however, it is Sweeney's Third String Quartet, from 2004, that has the word masterpiece stamped all over it. It is a monster of a piece lasting 36 minutes. It's totally abstract, and some might think it discontinuous, with its apparently fractured progression, pounding rhythmic unisons that dissolve, seemingly isolated and unrelated musical events, wild dances, and melancholic intensity. With a little familiarity, the events begin to cohere, and what emerges is a kaleidoscopic piece of a rare conciseness and almost Beethovenian intensity.