In Scotland in the early 1960s three events of consequence occurred, each of them marking a conspicuous turning-point in our local - and indeed international - musical fortunes. Though other commentators might look back on them differently, their influence on what had been until then a musically provincial country was profound.

First and second, almost simultaneously, Alexander Gibson founded Scottish Opera and Lord Harewood became director of the Edinburgh Festival, encouraging Scotland's own musical resources in a way his predecessors had not. Third, Thomas Wilson demonstrated that it was possible to be an important Scottish composer without needing to leave home, as his contemporaries Iain Hamilton and Thea Musgrave had felt compelled to do when they moved to America during the previous decade.

Though Wilson died six years ago aged 73, and has suffered since then a degree of the neglect that is often a deceased composer's immediate fate, there are signs that his music is deservedly reinstating itself. Certainly the performances later this week of his Violin Concerto by the National Youth Orchestra of Scotland in Glasgow and Perth, celebrating what would have been Wilson's 80th birthday, must count as a good sign. It was, after all, for a previous generation of NYOS forces, with Ernst Kovacic as soloist, that he composed the work in 1993 in memory of Bryden Thomson, conductor of the RSNO and a champion of Wilson's music, who had recently died.

Whether it is an elegy eloquent enough to outlive its immediate inspiration remains to be seen, but listening to Kovacic's recording, which was made at the time, suggests that the work has not lost its validity and stands ready for reappraisal.

Its single-movement structure, which owes something to Sibelius's last symphony, tautens the music's emotions, from the slow and dolorous opening pages right through to what the composer described as its "affirmative, even celebratory end", reflecting qualities Thomson manifestly possessed and Wilson was well able to capture as a composer. Now, at any rate, comes a chance to experience it again, this time with a different soloist, the American-born specialist in modern music, Kurt Nikkanen, but with a tighter travel schedule, which omits the visits to Aberdeen, Pitlochry, Birmingham and London previously included.

Concertos - he also wrote works for piano, viola and guitar, as well as a concerto for orchestra - formed a natural part of Wilson's output, and only his ultimately poor health stopped him writing a trumpet concerto for John Wallace and a trombone concerto for the maverick John Kenny.

The challenge of something different always attracted him, with the result that there is a wide range of fine Wilson works to choose between.

Born in Colorado of British parents, he came to Scotland as a child and spent the rest of his life in Glasgow as lecturer, reader in music and eventually professor in the university's extra-mural department. This gave him the ample scope he needed to compose, which he did in no uncertain manner, producing symphonies, concertos, operas, much choral and chamber music, upon which he lavished his skills.

The first of his five symphonies dated from 1956, at a time when the SNO's tired series of Austrian conductors - Karl Rankl, Hans Swarowsky - was seriously running out of steam. Two years later, with Alexander Gibson as eager catalyst, the orchestra was assembling a Scottish repertoire that would soon bring a new sense of purpose to its activities. Out went the constant repetition of Beethoven and Brahms. In came Wilson and everything he represented. Things were happening, soon to be symbolised by the founding in Glasgow of the autumn festival of Musica Nova, in which Wilson was represented alongside Iain Hamilton and Luciano Berio. Through him, the art of the Nordic symphony, established by Sibelius and Nielsen, was establishing itself in a Scottish format, sombrely coloured, structurally terse, emotionally (at least by Mahler standards) self-contained but not suppressed.

Even Peter Maxwell Davies, on moving to Orkney in the 1970s, suddenly started producing identifiably Nordic music, too little of which - other than the workmanlike Strathclyde concertos - has been performed on the Scottish mainland. Yet Wilson in Glasgow was, if anyone, the fountainhead of this development.

Edward Harper's now defunct New Music Group of Scotland was quick to take up his cause, along with that of other Scottish-based composers of the period. Glasgow University's McEwan concerts featured his chamber music, which included a tough, Bartokian, pungently uncompromising piano sonata, a cello sonata (in which, at one point, the cellist and pianist exchanged instruments) and a fine piano trio.

The Edinburgh Festival Chorus, founded by Lord Harewood in 1965, recognised Wilson's strengths as a choral composer - based like those of his successor James MacMillan on his deeply-felt Roman Catholicism - by commissioning his Te Deum for the opening of the 1972 festival conducted by Gibson. There was also from that time his powerful, disconcerting Mass for a Troubled World and, to complete the triptych, his Sequentiae Passionis, as evidence that he was not living in the past.

In was inevitable that Scottish Opera, too, would stake a claim in his inspiration by commissioning Confessions of a Justified Sinner as one of four Scottish works - the others were by Iain Hamilton, Thea Musgrave and Robin Orr - staged in the 1970s.

In recognising Hogg's novel as a suitable vehicle for operatic treatment, Wilson acted astutely. The split personality of the book's anti-hero cried out for musical treatment - sweet, euphonious music for one side of the character; abrasive, chromatic, discordant music for the other - and Wilson supplied it in spades. That the euphonious music represented the dark satanic side of the personality, the abrasive music the light, proved to be one of the nightmarish work's unexpected masterstrokes, vividly brought out by those admirable singers, Philip Langridge and John Shirley-Quirk, as the tenor and baritone aspects of the dual role.

Among the opera's telling strokes was the employment of Presbyterian psalm-singing, as when the tune of Martyrs was ominously voiced in Act One. A new production has been long overdue - the same can be said for its murderous predecessor The Charcoal Burner - but in Scottish Opera's current climate this seems unlikely. Yet of all his works it is the one I would most like to experience again. Perhaps the RSAMD's thriving opera school could do something about this.

The gradual atrophy of what had once seemed one of the great operatic periods in Scotland - where today are Musgrave's Mary Queen of Scots, Harper's Under the Greenwood Tree and Orr's Clydeside melodrama Full Circle? - is a symptom not of musical decline but of disgraceful Scottish Arts Council neglect, of which the collapse of Harper's music group, and others like it, forms part. It could not and would not have happened in Gibson's time.

When the Scottish Chamber Orchestra commissioned Wilson's fifth and last symphony shortly before his death, the resultant work was a keen-edged, kettledrum-obsessed masterpiece out of which could have sprung a new phase in his output. All that has happened, however, is the eclipse of much he had previously composed. His 80th anniversary looks like a good time to reassess his achievement. Let us hope it happens.

Thomas Wilson's Vioin Concerto will be performed by the National Youth Orchestra of Scotland at Glasgow Royal Concert Hall on Friday and the Perth Concert Hall on Saturday. Howard Williams will replace an indisposed Vernon Handley as conductor. The soloist is Kurt Nikkanen. His Chamber Symphony will be played by the RSAMD Chamber Orchestra under David Danzmayr at the academy on January 17 and the SCO plays Symphony No5 at Glasgow City Hall and Edinburgh Queen's Hall on January 18 and 19. Garry Walker is the conductor.