Some have hypothesized it to be related to Nahar and his illicit affair and henceforth a lover or child being fettered in the room. If that's what actually shown it would be unrealistic since no one ever goes there as per the information shared with us so far.
As some forum members had earlier suggested that the serial is inspired by Charlotte Bronte's novel 'Jane Eyre', which is possible but in the novel the screams of mentally ill wife are heard and one servant takes care of her. Hence the idea of a human living is improbable.
If the writers do show someone living it would be a major faux pas and disappointing too. 😕
Whatever the secret may be but going as per the story unwoven so far it leads us to believe that the singing should be related to the dark secret. It was in the temple where Tara first heard Saloni singing & she was mesmerized by her voice. Later the proposal for marriage was sent. The first meeting of Saloni with Nahar's family members is when she is asked to sing. Needless to say all appreciate it.
Also the secret is of the nature that it has potential to damage the marriage of Nahar and Saloni. Recently Kaki says Pia and Brijesh are involved so Tara too gets affected. That's why I think Kookie Kaki made the remark that the secret has potential to char all family members. 🤔
But since Brijesh and Nahar both get petrified at the mere mention of 'purani-dodi' it seems that its about much more than an affair perhaps a murder that implicates either of the brothers. 😲
Nahar goes to the room and may be the spirit of the dead possesses him for some time during late night and by morning leaves him. 😆
Of course the writers can mess it up 😆 but I do hope they come up with something convincing and innovative 🤔
Please share your views about this?