Recently I’ve had to memorise various piano pieces by Schubert. I find his music unusually hard to memorise, for a reason that throws light on why it is so profoundly satisfying.

Composers often use themes or musical material which they bring back later in the piece. Sometimes whole passages, whole pages of music come back. Usually when this happens it makes the task of memorising somewhat easier. But Schubert has a special way of bringing back material but changing it very subtly, so that it feels the same as when you first heard it, even though it actually isn’t. Mozart is the only other composer I know who has mastered this art to the same extent.

Sometimes superficial things change, like trills or other kinds of decoration added to phrases which didn’t have any when we first heard them. Sometimes octaves are added or taken away. Inner voices may be introduced, adding a quiet commentary to a returning motif. The same melody may come back, but with a different bass line, or with a new twist of harmony, leading to a new escape route and a new consequence. Sometimes a bit of music comes back but is compressed into a shorter span. Pauses or little rests may be introduced. Chords may retain the same harmonies as before, but reappear in different inversions. Something which was moderately loud in the original context is now reprised softly, or the other way round. A little four-bar digression may be extended to five or more bars when it reappears. A ‘legato’ phrase from the opening section may be non-legato in the closing one. A modulation to a distant key may be reprised with an even more adventurous modulation. Sometimes big things change, and sometimes the changes are so tiny that ‘only a real princess would notice them’.

Most composers use these techniques of variation to mark out a theme’s journey through a piece. But often their technique is plain to see when you study the score, and thus not too difficult to remember. The difference with Schubert (for me at least) is that he seems instinctively to grasp the way that memory works, and to translate the workings of human memory into music. In other words, he understands that we sincerely try to recall something as it was, and think that we have. But in fact we may have forgotten certain elements, or half-forgotten, or adjusted them unconsciously. Time and distance from the original event have rubbed away some of its contours, or made others stand out more vividly than they did. As we listen to Schubert’s music, we may feel that this was indeed the phrase as we first heard it, with all the same details. But it rarely is.

For the listener, all this happens so gently that they may feel they recognize things, just as they were, when they reappear later in the music. But in fact there is constant change. Schubert’s gift is to make this process feel natural, almost undetectable. Natural to listen to, that is  – but incredibly hard to memorise!