In Stockholm Crusell had become acquainted with the French ambassador to Sweden. This friendship encouraged and enabled him to undertake a trip to Paris in 1803. There he performed and also studied clarinet with Jean-Xavier Lefèvre at the newly formed Conservatoire. On 2 June, with the encouragement of Lefèvre, he purchased a new mouthpiece made by Michel Amlingue (1741–1816) and on 14 September a six-key C clarinet made by Jean Jacques Baumann. Before about 1800 Crusell had been playing with the reed turned up, but later turned it down, the modern practice and a position more compatible with cantabile playing. Exactly when he did this is not well established, but he may have favored the reed-above position because of a lack of evenness in his teeth.