There are believed to have been as many as 12 versions of the portrait, in which Bach is shown wearing an open jacket and holding the score for the Triplex Canon.
The best known of these, signed and dated 1746, is in the Altes Rathaus, Leipzig, although post-War scholarship and a series of restoration campaigns have questioned if, as long thought, it is the primary version painted from life.
The 2ft 8in x 2ft 1in (81 x 64cm) version of the portrait offered by Freeman's of Philaldephia on October 12 had been unearthed in Alabama by John Jones, Freeman's regional representative.
Once owned by Dutch aristocrat Baron Hendrick van Tuyll van Serooskerken, it reputedly travelled with the family to the Deep South from Germany via Holland in the 19th century and had been stored in a vault since 1966.
Haussmann-attributed paintings rarely appear on the secondary market, but Freeman's thought their picture, which had been relined and received a substantial degree of retouching, might bring $30,000-50,000.
In fact, it became the top lot of their Old Master sale when it brought $100,000 (£65,360). Bach was the object of a bidding war between a determined American buyer in the room representing an institution and two European telephone bidders.
The former, J. & J. Lubrano Music Antiquarians of Long Island, New York - dealers in all things pertaining to music, including manuscripts, books and rare printed music and now paintings - won the lot.
Exchange rate: £1=$1.53
