How was the sound that inspired Mozart? The Stadler Trio plays with two copies of basset horns made by Theodor Lotz, the great maker who worked with Anton Stadler and Mozart himself, and an original (first part) made by Raymund Griesbacher, the maker-performer who played in the basset horn trio of the brothers Anton and Johann Stadler. We cannot know how was the sound of the clarinets that pleased so much Mozart, but, probably, it would be close to the recordings you can download here. If you want to consider another possibility, you can listen to the Stadler Trio CD for Glossa, performed on three originals made by Theodor Lotz, very well preserved in Slovakia. Have a look at the signature and the n. 1, 2 & 3 (the instruments were designed to play in a trio). You can also see the rank of Lotz as an imperial supplier: K.K. HOF INSTRUMENTENMACHER/IN WIEN.
The basset horn trios (a sort of alto clarinets) played "Harmonie", i.e., arrangements for winds of the most celebrated parts of the contemporary operas, and original pieces, like the ones that Mozart, among many others, wrote for them.