I don't get the obsession with numbers here. Why 40?
I think its because there are about 40 school weeks in a year. i.e. it works out 1 piece per week.
And surely, not all pieces are equal in terms of how hard they will be to learn or how long they are. What counts as a piece - Tschaikovsky's Album for the young, for example: 1 piece or 40 (or whatever it is)? All in total shorter than a late Beethoven sonata, and a lot easier to learn.
And what does "learn" in this context mean anyway?
Yes indeed. Quite arbitrary. Although Ms Milne goes into a bit of detail about the definition of learn and the difficulty of pieces. Easier is upto 4 grade levels below (AMEB levels she's talking about) the exam the student is aiming for. In this way the student is more engaged by the variety of the tasks, and the pleasure of achieving something quickly, and their exposure to the repertoire is increased. And on the definition of learn, she says
" Near enough is good enough, but near enough means at tempo and with flow and with communicative intent, not a bald reading-through without any sense of what the music means. "
In her original post of the subject she says
"Many (most?) piano students around the world learn no more than ten pieces per annum. The idea seems to be that by investing all their energies into a smaller number of works the quality of the students’ performances will be enhanced. And at first glance this seems to be a reasonable idea.
But what happens is that students take longer and longer (in terms of days and weeks) to master an ever-smaller repertoire, and as the time-frames lengthen, and the repertoire lists shorten, so the student’s enthusiasm for practice seems to ebb almost entirely away."
And the point is
"Firstly, my students gain a wide, practical, lived experience of many distinct musical idioms and forms. Instead of learning one or two pieces from the Baroque period in a year, they may learn ten. Instead of mastering one piece in a swing groove, they may learn to play fifteen. <snip>
But most importantly of all, my students become very happy. In fact, I have observed a direct correlation between number of pieces learned and student happiness."