On 14 July 1790, the first anniversary of the Storming of the Bastille, a freedom celebration organized by Sieveking occurred in Harvestehude, a neighborhood of Hamburg, which received attention far beyond the city.
Together with his brother Heinrich Christian Sieveking, who was a year younger, he was taught by a private tutor, until both were sent to hear the mathematics lectures of Johann Georg Büsch at the Hamburg commercial academy in 1764.
Voght himself underlined this fact, when he wrote in a letter to all business partners in July 1793 that his friend had been the sole decision-maker of the firm for some years ("le seul gérant de notre commerce").
Some of the greatest role models of this circle around Sieveking were Gotthold Ephraim Lessing and Friedrich Gottlieb Klopstock, whom they gushingly admired as the composer of the Messias.
Sieveking and his friends saw their ideals put into practice when the French Revolution started in 1789, at least until the revolutionary idea of freedom was taken to absurd lengths by the Terreur of Robespierre.
Whilst the first anniversary of the storming of the Bastille was celebrated in Paris on the Champ de Mars, in Harvestehude in front of the gates of Hamburg a freedom festival took place, organized by Georg Heinrich Sieveking.
The firm had greatly profited from grain exports to France, and Gandolphe suspected that the celebration of Harvestehude had merely been staged to please the French and pave the way for further exchanges.
He finally countered the accusation that he was a Jacobin with an open letter with the title An meine Mitbürger ("To my fellow citizens"), in which he strongly denied having been pleased at the King's death.
In a letter to Magdalene Pauli, Voght wrote soberly in 1794: "Wie ein entzückender Traum schweben die Jahre 89 und 90 vor meiner Seele.
A number of merchants – including Sieveking – attempted to circumvent this rule by transporting their goods to the Danish port of Altona, and shipping them to France from there.
The relations between the Hamburgers and France, until then the city's most important trading partner by far, were still strong despite the prohibitions: this provoked the ire of Austria and its ally, Prussia.
At the end of 1792, he had founded a reading society in Hamburg with the journalist Friedrich Wilhelm von Schütz on the model of the Jacobin club of Mainz, of which Sieveking had been elected president, and for this reason alone was suspected of incitement.
His plan to support France's finances by raising the exchange rate for the mostly devalued assignats was rejected by the French as insufficient, and by the Hamburg Senate as impossible.
On 27 April, Sieveking received 300,000 Marks from the Hamburg Chamber of Commerce to be used at his own discretion, and he did not hesitate in using it to bribe Barras and other powerful figures of the Republic.