There is only one period documentation of the meeting between Bach and Weiss. In the Summer of 1739, Weiss followed Wilhelm Friedemann Bach home to Leipzig, where he stayed a month, and where "something extra fine in the way of music was taking place," according to Bach’s nephew Johann Elias.

A discovery in the 1990’s has shed light on the music performed during Weiss’s visit. The obbligato harpsichord "accompaniment" in Bach’s Suite in A for violin and harpsichord, BMW 1025, a work for which Bach’s authorship has always been questioned, even though he copied part of the manuscript, was identified as a literal transcription of Weiss’s Suonata in A, No. 22 in the "Dresden" Weiss manuscript. It follows that Bach is the likely composer of the violin part, and he probably did this during Weiss’s visit so he or his young son Friedrich (who copied the rest of the manuscript) could play with Weiss.

The informality and length of Weiss’s visit suggest that he already knew Bach well. They could, in fact, have met in 1717, when Bach played his first organ recital in Dresden, and Weiss already worked in the Hofkapelle (court orchestra) while awaiting confirmation of his appointment. Bach’s move is in 1723 to Leipzig, some 80 kilometers from Dresden, naturally increased their contacts. Surprisingly, the most important element which brought them together was not music, but the friendship of a popular professor at the University of Leipzig.

Germany in the early eighteenth century was a disunity of states under absolute rulers. As a city-state, Leipzig was a notable exception in its promotion of the freedom of learning. At the University, the poet J.C. Gottsched (1700—1766) championed the rationalistic philosophy of Christian Wolff (1679—1754), called "founder of the unextinguished spirit of thoroughness" by Immanuel Kant. The Wolffian ideal of "a complete synthesis of all human knowledge" with "the connectedness of mathematics" was Gottsched’s benchmark in his teachings and writings.

Bach was welcomed into Gottsched’s circle, and by 1727 had writen several cantatas based on Gottsched’s texts, including the much acclaimed Trauer-Ode, BWV 198. By 1732 Bach was privately writing harpsichord capriccios for Gottsched’s fiancée, Luise Adelgunde Victoria Kulmus (1713—1762). When she moved to Leipzig in 1735 to marry Gottsched, Bach referred his favorite pupil — J.L Krebs or the "one and only crab (Krebs) in this great brook (Bach)" fame — to be here composition tutor.

Luise Gottsched was a woman of extraordinary talents. She was a published poet. Her translation of Jospeph Addison’s writings on music into German influenced an entire generation of German music commentators. But her true love was the lute, on which "she played the most difficult pieces of Weiss almost at sight; also received the applause of this great master herself, when in 1740 he visited her…" Luise amassed an immense collection of Weiss’s music through the Leipzig bookseller Joseph Schuster — ther very "Monsieur Schouster" to whom Bach addressed his transcription of the Fifth Cello Suite on this program. Luise very likely owned and played this work too.

The Bach-Weiss friendship was a remarkable phenomenon in view of the two opposing camps of criticism of their music. Even within Gottshed’s circle, J.A. Scheibe, like Johann Mattheson, viewed Wolff as the "enlightner" who brought the illumination of the knowledge to the darkness of ignorance. For them, good music must possess a cantabile melody unobscured by excessive ornaments, angular intervals and above all, the other voices in the composition. Thus Scheibe attacked Bach’s works in 1737, accusing him of "darkening their beauty by an excess of art." The opposing school, led by Lorenz Mizler, saw the Wolffian universe as essentially mathematical, and music as "nothing less than a Geometry of tones." The charm of the style galant — exemplified by Weiss’s Suonaten — was for them superficial and irredeemable under the mathematical vigor of Wolffian scrutiny.

The Bach-Weiss summit of 1739 marks a turning point in both men’s careers. Undeterred by Scheibe and other critics, Bach went on to the glory of his final tyrilogy — The Goldberg Variations, the Musical Offering, and the unfinished Art of Fugue. Weiss reached the pinnacle of his career in 1744, when he became the highest paid Virtuoso of the Dresden Court.