Hannah told Global News: "My sister, who lives in LA, was clearing out her garage and she found a whole bunch of boxes. She wasn't looking for anything in particular. She was looking to do one of those pandemic clear-outs that we all did."
In one of the interviews, Lennon - who married Japanese artist Yoko in 1969 - admits to being "prejudiced" towards his own music when asked to name his favourite songs and goes on to discuss his creative process.
Hannah added: "I found that absolutely extraordinary and so insightful. Like, forget all those self-help books. John Lennon, just, like, puts it really well."
The tapes are now up for auction under the guidance of Omega Auctions and are expected to fetch up to $50,000.
Staff at Omega Auctions were quick to share their excitement over the historic discovery.
Paul Fairweather said: "Just reading the transcripts before we actually heard them was fascinating in itself. When we actually heard them, it was amazing to hear John speaking because they're such clear audio recordings that it feels that he's actually sat in the room with you."
The tapes will be auctioned off on September 28.