What is the meaning of the phrase "there was no one home" in this passage?

Question

Those who knew him in childhood remembered a lively, outgoing personality. Yet as time went by, while his music retained a boyish sparkle and vigour, he personally became more withdrawn and introspective as he dedicated his energies exclusively to composing and writing learned treatises. As one close friend put it: “His heart and soul were in the harpsichord; once he had shut its lid, there was no one home.”

Jean-Philippe Rameau: A Life

What is the meaning of 'there was no one home'? Shutting his mouth? secluding himself at the corner? retiring into his inner shell? No social contact?

Answer 1

The phrase suggests knocking on the door or ringing the bell of a home, but there is no one at home to answer the door. Someone wants to interact with the occupant, but there is no occupant present.

In this context, there was no one home suggests that the composer showed little or no interest in any aspect of life that was unrelated to the harpsichord. This suggests that he was emotionally absent, or at best just a passive observer, and would not interact with others. His emotional, mental, and social energy could be seen in his music, but not in other areas of his life.

Answer 2

Literally the phrase means that a house is vacant, that there are no people within.

Here it is used figuratively to mean that except when this person was playing the harpsichord, his personality was missing. He was withdrawn socially and showed little or no animation, particularly in comparison to his time playing music. It is as though he vacated his body, leaving behind a shell of a person.