As a child my sense of a regular beat was completely at the mercy of my awareness of the piano's incredibly rich sound. Relating to both at the same time was literally impossible, for the beat demanded control while the sound longed for its opposite.
In mid-adolescence, having given up on this impossible task, I "stopped" serious piano study to take up the organ. "The" problem disappeared, you might say. But it turns out that the problem is not generic, but for me, as for many individuals, specific to the acoustics of the instruments.
Given my rhythmic unsteadiness, much of the emphasis in my childhood lessons had been on keeping a regular beat. Later, when told that a passage was improvisatory I froze: After all those years drilling in the mathematical ratios of quarters and sixteenths how was I to stop counting and let the line simply move as if on its own?
It is a question of chickens and eggs, since the two are obviously so closely intertwined. But not everyone can accept their close intertwining. The more fragile of the two elements is surely tone for it is a quality separate from pitch, and cannot be written down. Almost everything in our culture conspires against awareness of the specificity of tone quality now that we have succeeded in digitizing almost everything but not the piano.
Kurtag's solution to rhythm notation in the early stages is to use a kind of shorthand: this symbol is more or less long, the other, short. That symbol is a pause, the duration of which is up to you. This way the child is free to feel rhythmic relationships within a context of tone logic and the flow is neither threatening nor confining.