I was interested to discover that, like Mozart and Bach no less, Vaughan Williams' instrument was the viola. The viola? The instrument that has as many jokes made about it as Skoda cars do? Even though Amadeus may have been an exercise in fascinating historical fiction, no one could accuse Mozart of being uninterested in high-visibility showmanship. Vaughan Williams was not like that, and yet anyone who's heard the Fantasia on a Theme of Thomas Tallis would be forgiven for knowing that RVW was a string player.But though the viola does make a beautiful sound, it's possibly the most invisible in the orchestra, because its timbre blends with the violins and the cellos, and is neither the highest, nor the lowest. Rarely does the viola get a tune you could sing, nor is it the underpinning bass that defines the harmonies: the joke about what you call a violist at the bottom of the sea ("a start") is only one of the many which other musicians tell about how dispensible it is.
So why did it appeal to at least three great composers? (I've been watching RVW rising back up the approval ratings in the wake of the 50th anniversary of his death). I think it must be to do with it being one of the most important elements in what musicians call the inner parts: alto and tenor lines, clarinet and bassoon parts. If you like, a tune is like a story: the thing we first want music to give us, the sine qua non, the thing we whistle so that others can recognise what we're talking about. But, as the art develops, what happens to a tune - how that plain statement is supported, given texture, qualified, changed, synocopated, undermined, shifted into the minor, the dominant, the unexpected - becomes an ever more interesting business. In modernism, for instance, the original element of storytelling/tune is taken as - literally - read, in that the reader/listener is given everything except a coherent version of that original element, which they must put together from all the other elements, including the inner parts.
Which doesn't mean that a wonderful tune isn't still one of the best small things that can happen to a human being. Nor that both Mozart and Bach and RVW wrote some of the most exquisite tunes that have ever existed. But maybe that's why the question 'What's your book about?' is so hard for novelists to answer. Because there are so many answers, so many textures, rhythms, harmonies and counterpoints to talk about, and "the Princes in the Tower" is only one of them.