Opera and history buffs and the simply curious can pay $125 a head for an unprecedented gawk inside what was the diva soprano's haven from 1912 until her death in 1931.

Melba jazzed-up a modest farmhouse into an elegant, nine-bedroom country spread packed with furniture and objets d'art from her travels.

Visitors will take tea, sip wine from Coombe's vines and hear stories from Melba's life in her music room with its bay windows, parquet floor, French chintz sofas and Chinese porcelain vases.

It was here, beside her baby grand piano, that she performed for visitors including prime minister Billy Hughes, English actor Ellen Terry and artists Hans Heysen and Arthur Streeton.

In the bathroom, the bath is hidden behind a wardrobe door, and the toilet is playfully designed to look like a chair.

Visitors will wander around Melba's French-style "boudoir" or private office, where an appointment, "to hear a little girl sing", is written in fountain pen in a diary.

An exquisite ebony and ivory writing box sitting on a bureau was given to Melba by author Leo Tolstoy on a trip to St Petersburg, Russia.

In Melba's bedroom is a vivid Belgian Blue glassware set, her Hermes riding boots, and a cameo picture of her son, George, as a boy.

There is also a simple painting of the ocean that she hung in in her rooms wherever she travelled, to remind her of far away Australia.

The hour-long tours of 10 people at a time, on from July 6 to August 13, aren't cheap, but estate manager Daniel Johnson said it was part of a move by the mansion to pay for its own upkeep.

In 2014, three years after the death of Melba's granddaughter Pamela, or Lady Vestey, the garage and stables were converted into a 150-seat restaurant, museum and cellar door.

Starting guided tours of the 2.8-hectare garden, designed by William Guilfoyle​, has proved a success, with 15,000 visitors in the past financial year.

Mr Johnson said in the past, Melba's private rooms, "would have only ever been seen by friends and family, not open to the public at all".

The house tours responded to public demand and would provide Melba's great grandsons, the UK-based Lord Samuel Vestey and the Honourable Mark Vestey, with a way to preserve Melba's legacy.

Mr Johnson said it was "a once in a lifetime opportunity to see behind the curtain and share in the theatre of Melba's life. You're walking in the footsteps of the world's greatest diva."