John Lucas dedicates his book - the fullest, fairest account of the great conductor's life to have yet appeared - “to the countless musicians who helped Beecham make us a more musical nation”. That is precisely what Thomas Beecham did, in a career that began in 1899, when he was 20, and ended 60 dazzling, controversial years later.

Lucas's record of what this son of a Lancashire industrialist achieved by his genius and energy is prodigious: the orchestras founded, two of which, the London and Royal Philharmonics, are still going strong; the standards of performance transformed out of recognition; the new music championed (Richard Strauss, Stravinsky, Sibelius, Delius), the old music rediscovered; the enormous repertoire, the mastery of a huge range of musical styles; the passionate dedication to opera in a country that was an operatic no-man's- land when he first burst on the scene; not least, what he did to make the stage works of his beloved Mozart known to his unsuspecting fellow citizens. Beecham was also the first British conductor to become famous abroad.

But Lucas is right, too, to emphasise his subject's electric impact on the musicians who came under his spell and found themselves changed by it. He was a musician's conductor. There is a story (a true one, not told in this biography, rich though it is in anecdote) of Beecham in old age at the end of a rehearsal with the Royal Philharmonic (RPO) in Oxford, where they used to repeat programmes given earlier in London. “We don't have a symphony this afternoon, do we?” “Yes, Sir Thomas, the Second of Brahms.” “Ah well, we all know that little piece, don't we?” A young second violin raises his hand: “Sir Thomas, I've never played it.” “My dear fellow, there's no need to worry. I can assure you you'll like it - it's charming.”

Imagine that happening at a rehearsal by Toscanini or Fritz Reiner. The culture of Beecham orchestras was different. To quote the composer Malcolm Arnold, who played trumpet under him, “Unlike so many of the big names, he had the ability to make a player feel that what he was doing was worth while. His musical standards were of the highest but he never made the players feel they were beyond them.” He knew them and treated them as individual human beings; he gave them freedom to express themselves.

The CD of Beecham rehearsing the RPO that comes with the book shows him, in his late seventies, relaxed, unbuttoned. But by all accounts there was the same camaraderie in the days when he laboured to transfigure the rough-and-ready standards of British orchestral playing. From the first the results were spectacular, as testimony cited by Lucas demonstrates: “Never in England, indeed only in Vienna under Mahler, had I heard music rehearsed to such a peak of perfection” (Ethel Smyth, 1909); “I've never heard such marvellous sounds anywhere as this amazing orchestra revealed in my scores” (Stravinsky, 1912).

If the players loved him, the stuffed shirts of the Establishment were deeply distrustful of his endless schemes (“divergent views were expressed by the board as to the reliability of Sir Thomas's statements”): Beecham was a mountebank, more a “character” than a serious musician (this of a thorough-going professional whose brilliance was founded on sheer hard work), a man recklessly generous with other people's fortunes as well as with his own.

He could be outrageous - rude, tactless, publicly abusing as philistine nonentities the very people whose support he needed to fulfil his mission. Lucas calls him “a natural dissembler”. His private life was frequently chaotic: only two marriages but a succession of often flamboyant and overlapping affairs. His quixotic nature was roused by the unconventional - as when, discovering “that a performance of Carmen at the [New York] Met to which he had invited a party of young Australian airmen was sold out, he arranged for them to watch it from the wings, where...they joined in the better-known choruses”. Often he would waive his fee, even when near bankruptcy. He certainly treated the great and the good with far less respect than he did his players.

They repaid him. His exertions had saved musical life in Britain during the 1914-18 war. But when, after the second world war, it started up again, he was cold-shouldered, consulted neither about the reopened Covent Garden nor about the newly built Festival Hall. In 1930, reviewing a Beecham Meistersinger in Cologne, the critic Richard Capell had felt shamefaced “at the thought that at home a proper sphere of action is still denied this rare spirit who (can it be questioned?) is so far and away the finest musician our race and generation have produced in the executive field”. Nothing changed. Beecham's triumphant series of opera performances in Buenos Aires in 1958 was, in Lucas's words, “the ultimate irony of his life”: that, at the age of 79, he “had to travel 7,000 miles to conduct a season that he could have been offered in London”.

In telling the story of the provincial pill-millionaire's son who transformed himself from a “shy, groundward-glancing little figure” (as the composer Cyril Scott described him) into “a figure of such force and magnetism that the whole of musical England was to feel its grandiose effects”, Lucas makes clear how criminally misguided the great and good were and how much, despite them, we all owe him.

Thomas Beecham by John Lucas
Boydell Press £25 pp388

Times Recommends

• Superfreakonomics by Steven D Levitt and Stephen J Dubner
• The Times picks the 50 best paperbacks of 2009
• Vincent van Gogh’s letters show the soul of the artist