For historically informed performance of the Mozart Concerto, Quintet and late operas, this is a speculative reconstruction of the basset clarinet used by Anton Stadler and pictured on his now well known Riga concert program from 1794 (see below).
In the absence of any exact original examples, it is based on an amalgamation of two specimens-
- a 5 key clarinet in A by Kaspar Tauber of Vienna (Nicholas Shackleton collection), whose clarinets were very similar to those of Theodor Lotz, the builder of Stadler's clarinets prior to 1792;
- for the extended range section, a basset horn in F by Johann Georg Braun of Mannheim (Universität Leipzig Musikinstrumenten Museum), as described on this site, which is from a somewhat later date but very closely matches the drawing of Stadler's clarinet.
It has a minimum of keys in the upper sections (though more can be requested), a chromatic extension to low C and a bulb-shaped bell (which we now know, from examination of the Braun basset horn as well as from the Riga drawing, should point backwards).
Low B below bottom C is playable if the vent hole in the bell elbow joint is closed by pressing it against the leg; at least two passages in the Mozart Concerto (1st mvt. bar 295 and 3rd mvt. bar 147) seem to require this. A key for low B as on the Braun basset horn would be possible, but it does not appear on the Riga drawing.
normal tonality is A, but Bb is also available. The usual pitch is