No, he doesn't harvest music!
One must work at it, but do not aim at it directly. Let the heart not forget, but do not help it grow. Do not be like the man from Song (Sung). Among the people of the state of Song there was one who, concerned lest his grain not grow, pulled on it. Wearily, he returned home, and said to his family, 'Today I am worn out. I helped the grain to grow.' His son rushed out and looked at it. The grain was withered. Those in the world who do not help the grain to grow are few. Those who abandon it, thinking it will not help, are those who do not weed their grain. Those who help it grow are those who pull on the grain. Not only does this not help, but it even harms it.
This parable appears in the middle of a larger fragment, Mengzi (Mencius) 2A2 (Bryan Van Norden, trans.). The standard interpretation these days (e.g. P.J. Ivanhoe) is this. Just as the man of Song harms his grain by trying to force it to grow, so also we can harm our moral development by trying to perform grand acts of morality before we are psychologically ready to do so -- i.e., before we'd feel happy and unresentful doing so.
Two considerations may seem to compel this interpretation. First, Mengzi often uses agricultural metaphors to talk about the cultivation of moral goodness. And second, the sentence preceding the parable is: "Consequently, I say that Gaozi never understood righteousness, because he regarded it as external." Hence, the "it" at the beginning of the parable might naturally be understood as "righteousness".
But here are two problems: First, its plausibility. It seems strange to say that "Those in the world who do not help the grain [i.e. morality] to grow are few." Are people generally as eager to work at becoming more virtuous as this farmer is to help his grain? And furthermore, is trying to force oneself to be virtuous such a bad thing? -- something that generally harms one's moral development?
Second, Mengzi never says, anywhere else, anything like "That would be a morally good thing to do, but you would resent doing it, so you shouldn't do it. Take it slow, instead." On the contrary, Mengzi seems to demand instant moral behavior from everyone and is unsatisfied with half-measures (e.g. 3B8, 7A39, 1A3).
A better interpretation of the parable, I think, comes from looking at 2A2 as a whole. 2A2 begins with long discussion of the "unperturbed heart", the "floodlike qi [breath/vital-energy]", and courage. The kind of courage Mengzi most admires is strength of moral conviction (which seems to be the core of "sageness", e.g., in 5B1) -- not being blown about by the winds of circumstance and drawn away from one's convictions by the temptations of personal advantage. If no circumstance, good or bad, could perturb your heart and interfere with your breath [qi], then you will be unshakeable from morality: This is having a "floodlike qi". Immediately before the parable of the farmer is this:
Gongsun Chou said, "I venture to ask what is meant by 'floodlike qi.'"
Mengzi said, "It is difficult to put into words. It is a qi that is supremely great and supremely unyielding. If one cultivates it with uprightness and does not harm it, it will fill up the space between Heaven and earth. It is a qi that unites righteousness with the Way. Without these, it starves. It is produced by accumulated righteousness. It cannot be obtained by a seizure of righteousness. If some of one's actions leave one's heart unsatisfied, it will starve. Consequently, I say that Gaozi never understood righteousness, because he regarded it as external."
In this broader context, I'd suggest the parable is not about the cultivation of morality or righteousness per se but rather about the cultivation of a floodlike qi -- i.e., steadfastness of character. Plainly this is related to morality for Mengzi, but it is not the same.
What is it, then, to try to force one's character to grow, per the farmer of Song? Maybe this: Overestimate one's steadfastness. Allow oneself to be put into situations that bring out the bad in people, thinking that you can resist in a way others can't -- allowing yourself that "one more drink", saying to yourself "I won't yield to temptation this time", or "politics won't corrupt me", or "if I get [money, power, influence, the promotion, etc.] I won't be like those other people". There are few of us who don't overestimate ourselves in that way; and so overestimating ourselves we put ourselves in situations that greatly harm our moral character.
This interpretation, although only subtly different from the standard, is different enough to avoid the latter's difficulties.