SHE is one of the most generous but also largely unknown figures in Scottish culture, a woman described as a "model 21st-century philanthropist" who rarely, if ever, speaks in public.

Now Dr Carol Colburn Grigor, who through her Dunard Fund has given more than £20million to the arts in Scotland, including £8m to the Edinburgh International Festival (EIF) alone, has been honoured publicly by the festival for the first time, at the opening concert of this year's programme.

Mrs Grigor, the Chicago-raised but Edinburgh-based former concert pianist, was announced last night as the new honorary vice president of the EIF.

Today the festival season in Edinburgh moves into top gear, with not only the EIF beginning, but also the Edinburgh International Book Festival starting, with appearances from Salman Rushdie and Roddy Doyle today.

At the opening concert of the 67th EIF, director Sir Jonathan Mills said Dr Grigor's contribution to the Scottish and UK arts scene had been "simply astonishing".

Mrs Grigor very rarely gives interviews and Dunard Fund donations are usually unspecified, although it disperses more than £2m a year. It has provided vital financial support over several years to the Scottish Chamber Orchestra, Scottish Opera, Dunedin Consort, the National Galleries of Scotland and Edinburgh's Festival Theatre.

In 2006, the Fund gave the EIF £500,000 so it could clear its debts, which at one point had risen to £1.5m.

She once said: "Some people's hobbies are buying expensive race horses or whatever. Our hobby is giving."

Last night she said: "I am deeply honoured, and look forward to working with Valery Gergiev, Jonathan Mills and his successor Fergus Linehan towards continuing a hugely vibrant and successful International Festival."

Sir Jonathan said: "For the past 66 years the Edinburgh International Festival has been extremely fortunate in the range and diversity of passionate advocates devoted to its success and well-being.

"Those that work for the festival are deeply indebted and fired by these rare and remarkable individuals who derive pleasure from sharing their 'love of humanity' through their philanthropy with the rest of us."

Mrs Grigor's father, Richard D Colburn, built up a multi-million dollar electrical company in the US, but he was also a viola player who gave money to Los Angeles' leading music school.

Sir Jonathan added: "The depth of Mrs Grigor's contribution to the visual and performing arts, and particularly to music and opera, throughout the UK but especially in Scotland, is simply astonishing.

"With characteristic self-deprecation Carol explains her behaviour in terms of genetics; suggesting that she was born with the 'giving gene'. It is our honour to have her accept this role as honorary vice president."

Last night's opening concert at the Usher Hall was Prokofiev's film score for Eisenstein's Alexander Nevsky.

The Royal Scottish National Orchestra and the Edinburgh Festival Chorus were conducted by Valery Gergiev.

Mrs Grigor, who performed as a touring concert pianist in Edinburgh 30 years ago, gave up her career as a musician when she married Jens Hogel, a UN official.

They came to Edinburgh on business and in the 1970s bought Dunard House in Perthshire, after which the trust is named.

The couple later divorced, but Mrs Grigor stayed in Edinburgh where her children were raised.

Mrs Grigor has been recognised before, with a Commander of the British Empire (CBE), a recipient of the Prince of Wales Medal for Philanthropy, and the Chevalier de l'Ordre des Arts et des Lettre.

This year's EIF has the theme of technology, and features several sold-out events, including the Bavarian Radio Symphony Orchestra concerts at the Usher Hall, Faure's Requiem and Verdi's Requiem.