A trove of Freddie Mercury's previously unseen handwritten draft lyrics for some of Queen's biggest hits goes on show Thursday in New York, ahead of their sale in London later this year.

The manuscripts include working drafts for "Bohemian Rhapsody" — which Mercury initially planned to call "Mongolian Rhapsody" — "Don't Stop Me Now" and "Somebody to Love".

"In scope, quality and exceptional provenance, the collection of lyrics together afford an unprecedented glimpse into the creative mind of one of the 20th-century's most influential songwriters," said Sotheby's, which is staging the auctions in September.

More than 1,500 items from Mercury's private collection, including costumes and unique objects as well as the draft lyrics, will feature in the eventual auctions in London and online.

Left largely untouched at his former West London home in the three decades since his death, they will be sold at live events in the British capital on 6-8 September and online from 4 August to 11 September.

The vast array of items — being auctioned by Mary Austin, one of the icon's closest friends who has cared for them at his former home Garden Lodge — is expected to fetch at least £6 million ($7.5 million).

A highlight of the trove unveiled Thursday is 15 pages of lyrics and melodies that led to "Bohemian Rhapsody", one of Queen's most globally beloved and streamed songs and the third best-selling UK single ever.

Written in black and blue ink and pencil, on stationery from the now-defunct British Midland Airways, they reveal Mercury originally planned to call it "Mongolian Rhapsody".

The songwriter, who died in 1991, had at some point crossed out the word "Mongolian" and replaced it with "Bohemian".

The 15 pages are expected to fetch up to £1.2 million at the auction.

Other draft lyrics going on display include nine pages of lyrics for arguably Queen's greatest anthem, "We Are The Champions", 19 pages behind 1976 hit "Somebody to Love" and seven leaves for "Don't Stop Me Now".

Meanwhile, a red notebook from the early 1970s, before Queen was signed as a band and believed to be Mercury's earliest known containing lyrics, will also be on show in New York until June 8.

"Freddie Mercury's spectacular performances and songs are rightly remembered and celebrated around the world," said Gabriel Heaton, Sotheby's books and manuscripts specialist.

"However, thanks to the emergence of this extraordinary group of early handwritten lyrics we can now also fully appreciate the absolute skill as a lyricist which complemented his consummate showmanship."

Heaton added it cemented "his standing as one of the greatest songwriters of his generation — and beyond".

The collection of draft lyrics and other items will be in Los Angeles June 14-18 and Hong Kong June 26-30 before arriving in London August 4 for a month-long exhibition ahead of the auctions.