James Fenton has a rather irresistible little essay in the Guardian Review about taking the grade five music theory exam as an adult en route to further study of the piano:
The first thing you find, as an adult student (assuming you have a good teacher, a matter in which I have always been lucky), is that the very first thing you do is deeply interesting.
That is, the very first thing you do is try to play a note well, and this business of trying to play a note well is what is going to absorb your attention forever after. You do not begin by learning how to play a piece badly, and later, at an advanced stage, become inducted in the method of playing it well. You start with your ulterior purpose in plain view. In this sense, you are treated as an adult.
Which is most important: what horrifies the adult student is the prospect of a second childhood at the keyboard (Mrs Curwen's Pianoforte Method, and the immortal music of Joan Last and Adam Carse). The faintest hint of condescension in music makes it intolerable to the adult: anything with English nursery rhymes, anything programmatic (that is, descriptive pieces with titles like "Going Up the Stairs" or "Putting Teddy to Sleep") is repulsive. And it would continue to be repulsive even if the titles were chosen some-how to reflect the ups and downs of adult life: "Taking Crystal Meth", "Putting Your Back Out", "Stepping in Something Nasty" would be, once the novelty had worn off, just as bad, viewed as elementary piano pieces. They would share the same mimetic quality, the same sense that the abstract pill of music has to be sugared for the beginner.
That is what is so good about Bartok as an elementary composer. I have often heard people say that the first two books of "Mikrokosmos" are a bore to listen to, and maybe they are. But they are never a bore to play. They are like a serious invitation to self-discipline. You can bring as much ambition to them as you please, in the matter of producing a beautiful sound by striking a series of notes.