A handwritten manuscript for Mozart's Contredanse in C for Orchestra "La Bataille" will sell at Sotheby's.
It's valued at £500,000-700,000 ($704,150-985,810).
The piece dates to 1788 and is one of only a handful of complete works by the composer to come up for auction.
Mozart wrote it while he was serving as official composer to the court of Joseph II in Vienna. While less well known than his earlier works, these later dance-oriented pieces are still celebrated.
Sotheby's comments: "The autograph is written, with relatively few corrections, in the beautiful, fluent script of Mozart's maturest period."
The record for a handwritten piece of Mozart sheet music is $4.3m, set for a 500 page manuscript containing nine scores at Sotheby's in 1987.
A first edition copy of JS Bach's Clavier Ubung (part two) is offered with an estimate of £120,000-150,000 ($175,559-219-449).
The book is one of 15 recorded copies and the only one to still remain in private hands.
It contains a number of annotations, which could possibly be in Bach's own hand. It's difficult to be sure, as the markings are small (a couple of rests and alto clefs).
Sotheby's describes it as "one of the finest copies of a Bach first edition that we have seen."
The sale will take place in London on May 24.
Please sign up to our free newsletter to receive exciting news about music memorabilia auctions.