The “musical instrument” is a joke of Mr. Robinson’s. He constructs a loom for his wife, using two strong reeds for the frame and cutting up smaller reeds for the teeth of the comb. He gets his sons to help with this task but does not tell them what it is that they are making. When they finally put the loom together, the children still have no idea what it is, so their father tells them that it is “an outlandish sort of musical instrument” and that their mother will understand how to play it. After this, the children always refer to their mother’s weaving as “playing the loom.”

The Swiss Family Robinson is not noted for its humor. There is a strong atmosphere of moral earnestness pervading the book, reminiscent of a religious tract. Even this very mild joke actually goes against the principles Mr. Robinson has formerly expressed. When Fritz pretends that his hunting expedition has been unsuccessful and then, having fooled the family, reveals the sucking pig he has shot, Mr. Robinson says that he is glad to see the result of his son’s prowess but “cannot approve of deceit, even as a joke.” He tells Fritz rather priggishly that he must always tell the truth, “in jest and earnest.” However, Mr. Robinson seems to have forgotten this precept here.