If you have always wanted to know: (a) what music is, (b) what music does, (c) what music means, you're in luck. You will probably find an answer in a newly published book. I say "probably" because this book offers multiple definitions of what music is, numerous explanations of what music does and frequent contradictions of what music means. In other words, something about music for everyone.

The book is "An Encyclopedia of Quotations About Music." Gathered from hundreds of sources and edited into a quickly digestible format by Nat Shapiro and published by Doubleday, it is an exhaustive compilation of opinions and descriptions of music that may amuse, irritate, outrage or delight you. In it, you can easily find something that proves irrefutably right any opinion you have always held.

For instance, here are some answers you might like to one of the questions many musicians are often asked. "Just exactly what," they are asked, "is music?" Shapiro's book, which will from now on be referred to as AEOQAM, fully enlightens those questioners. "Music is an outburst of the soul." That one comes from Frederick Delius. "Music is the eye of the ear." Now that's a big help. Thomas Draxe thought it up in 1616.

If neither of those helps you much, this is bound to: "Music is the most disagreeable and the most widely beloved of all noises." That was dreamed up in 1863 by Theophile Gautier, the man who came up with the idea for the ballet "Gisella," and one of the great early writers on dance. Victor hugo said music was "the vapor of art," while Charles Kingsley, unwilling to be outdone by smaller minds, modestly claimed music as "the speech of God himself."

Kingsley would find himself in strange territory if he talked about music to Yip Harburg, who said in 1973, "Music today is money, that's all. It's rhythm, it's hypnosis, it's a good deal of hysteria and a lot of complaint." 1973 was three years after Jerry Rubin said, "Rock music must give birth to orgasm and revolution."

Composers can be of as little help to laymen in talking and writing about music as noncomposers usually are. But remember, when composers discuss music, you are hearing from experts in the field, no matter how widely their views may differ.

"What does it mean?" people are forever asking composers. Aaron Copland says, "The whole problem can be stated quite simply by asking, 'Is there a meaning to music?' My answer is that would be, 'Yes.' And 'Can you state in so many words what the meaning is?" My answer to that would be, 'No.'"

Igor Stravinsky wrote, "If, as is nearly always the case, music appears to express something, this is only an illusion and not reality." But Richard Strauss said, "There is good music and bad music. If it is good, it means something, and then it is Programme Music." Fine - but what it mean ? And did Stravinsky help things at all when he said in a lecture at Harvard University, "I hold that music is given to us to create order"?

Ned Rorem, who has written about music more than any other living composer, puts it bluntly - and correctly: "The hardest of all the arts to speak of is music, because music has no meaning to speak of." Then there is James Huneker's pungent note on Wagner, voiced in 1913: "Wagner, thank the fates, is no hypocrite. He says what he means, and he usually means something nasty."

Perhaps you have always thought that the world's famous conductors sweet-talked their musicians in order to get them to play more beautifully, more accurately or simply better. Sir Thomas Beecham, not to disillusion you, once told a troublesome musician during rehearsal, "We do not expect you to follow us all the time, but if you would have the goodness to keep in touch with us occasionally . . ."

Arturo Toscanini, some of whose more historic outbreaks of temper were secretly recorded during rehearsals, was less delicate than Sir Thomas. In fact, he was probably the least delicate man in the whole history of rehearsal. Displaying a special inside knowledge of his players, he threatened them: "After I die, I shall return to earth as the doorkeeper of a bordello, and I won't let a one of you in." There exists no certain evidence of what effect that promise had.

Shapiro has done his best to include as much humor among his quotations as he could find. He has this beaut from what some may consider an unexpected source, Artur Schnabel: "Have I a secret about playing the piano?" the great pianist once answered an inquiring reporter. "It is a very simple one. I sit down on the piano stool and make myself comfortable - and I always make sure that the lid over the keyboard is open before I start to play."

Schnabel is also the source of a remark I always wish I could remember when correspondents write in to complain because some members of an audience do not remain in the hall to insist upon encores. "Applause," said Schnabel, "is a receipt, not a bill."

It is always important to remember that everything that today may be said against new music by those who are out of sympathy with it has been said in the past. For example, in the 17th century Samuel Scheidt felt strongly: "Music is now so foolish that I am amazed. Everything that is wrong is permitted, and no attention is paid to what the old generation wrote as composition." Scheidt was writing before Bach and Handel had been born!

By the time you have waded through the differing opinions, the hyperbole and floweriness that fills AEOQAM, you will be ready to be comforted by the essential truth of comments from two great musicians: Aaron Copland wrote, "Music is in a continual state of becoming." And Sergei Rachmaninov said what has become my motto: "Music is enoughfor a lifetime - but a lifetime is not enough for music."